Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Ex Input:
Context: Elements form compounds when they combine chemically. Their atoms join together to form molecules, crystals, or other structures. The atoms are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions. It occurs when atoms share or transfer valence electrons. Valence electrons are the electrons in the outer energy level of an atom. You can learn more about chemical bonds in this video: MEDIA Click image to the left or use the URL below. URL: Look at the example of water in Figure 7.1. A water molecule consists of two atoms of hydrogen and one atom of oxygen. Each hydrogen atom has just one electron. The oxygen atom has six valence electrons. In a water molecule, two hydrogen atoms share their two electrons with the six valence electrons of one oxygen atom. By sharing electrons, each atom has electrons available to fill its sole or outer energy level. This gives it a more stable arrangement of electrons that takes less energy to maintain. Water (H2 O) is an example of a chemical compound. Water molecules always consist of two atoms of hydrogen and one atom of oxygen. Like water, all other chemical compounds consist of a fixed ratio of elements. It doesnt matter how much or how little of a compound there is. It always has the same composition. Elements are represented by chemical symbols. Examples are H for hydrogen and O for oxygen. Compounds are represented by chemical formulas. Youve already seen the chemical formula for water. Its H2 O. The subscript 2 after the H shows that there are two atoms of hydrogen in a molecule of water. The O for oxygen has no subscript. When there is just one atom of an element in a molecule, no subscript is used. Table 7.1 shows some other examples of compounds and their chemical formulas. Name of Compound Electron Dot Diagram Numbers of Atoms Chemical Formula Name of Compound Hydrogen chloride Electron Dot Diagram Numbers of Atoms H=1 Cl = 1 Chemical Formula HCl Methane C=1 H=4 CH4 Hydrogen peroxide H=2 O=2 H2 O2 Carbon dioxide C=1 O=2 CO2 Problem Solving Problem: A molecule of ammonia consists of one atom of nitrogen (N) and three atoms of hydrogen (H). What is its chemical formula? Solution: The chemical formula is NH3 . You Try It! Problem: A molecule of nitrogen dioxide consists of one atom of nitrogen (N) and two atoms of oxygen (O). What is its chemical formula? The same elements may combine in different ratios. If they do, they form different compounds. Figure 7.2 shows some examples. Both water (H2 O) and hydrogen peroxide (H2 O2 ) consist of hydrogen and oxygen. However, they have different ratios of the two elements. As a result, water and hydrogen peroxide are different compounds with different properties. If youve ever used hydrogen peroxide to disinfect a cut, then you know that it is very different from water! Both carbon dioxide (CO2 ) and carbon monoxide (CO) consist of carbon and oxygen, but in different ratios. How do their properties differ? There are different types of compounds. They differ in the nature of the bonds that hold their atoms together. The type of bonds in a compound determines many of its properties. Three types of bonds are ionic, covalent, and metallic bonds. You will read about these three types in later lessons. You can also learn more about them by watching this video: (7:18). MEDIA Click image to the left or use the URL below. URL: Chocolate: Its been revered for millennia by cultures throughout the world. But while its easy to appreciate all of its delicious forms, creating this confection is a complex culinary feat. Local chocolate makers explain the elaborate engineering and chemistry behind this tasty treat. And learn why its actually good for your health! For more information on the science of chocolate, see [Link] . MEDIA Click image to the left or use the URL below. URL: 
 Question: force of attraction between atoms or ions that share or transfer electrons

Ex Output:
chemical bond


Ex Input:
Context: Saturday, October 8, 120 miles northeast of Blainsworth, Nebraska; 1:16 p.m.Bob Irisin, a metrologist for the Kansas City weather bureau, is riding in his Bronco truck when he stops and radios to his friend Stan in Kansas City, that he is witnessing a sudden change in weather patterns in the area. Then a tornado suddenly touches down near a farm where Bob sees a family of a man, woman and their little girl standing in front of the house, unaware of the tornado approaching behind them. Bob drives as near as he can go and manages to yell out a warning to the family seconds before they see the twister coming. The family runs into their storm shelter just in time before the twister destroys their house. Bob drives away from harms way just in time.Meanwhile, in Blainsworth, there is the annual fall Bike-a-thon race for the high school kids. 13-year-old Dan Hatch gets a flat tire and doesnt come in at all. Dans stern father, Jack, is arguing with a banker who's asking to foreclose on his hardware shop since a new mall has opened in the nearby town. Jack refuses to sell the shop at any price. Dan walks his bike into the town square where his best friend, Arthur, talks with him about getting "crashed and burned" during the race. Jack walks over and becomes hard on Dan for not finishing the race like a man should. Dan yells at his father for being so demanding and that he can't expect anything from anyone. Dan's mother, Laura, with her new baby Ryan and her friend Jenny, walk by and never less tell him he did okay anyway. Just then, Dan is called to the square podium for he is has been chosen by a lottery to be the winner of a new Schwinn Voyager bicycle, much to his father and mother's delight.75 miles northeast of Blainsworth; 3:37 p.m. Bob sits in his Bronco truck and radios in of rogue weather patterns, while observing another tornado rip through a nearby trailer park. Bob tells Stan that the front is moving south instead of north and the atmospheric activity is the most bizarre he has ever seen. Bob decides to travel to Blainsworth to see if anything will happen.Outside of Blainsworth, Dan and Arthur sit in the woods looking up at the clear sky. Dan tell Arthur about his fathers demanding which is a driving force that he cant stand. Then Arthur's two younger sisters, Stacey and Ronnie Vae, appear and want Arthur to come home since their parents are out of town for the weekend. Arthur and Dan watch as clouds begin to roll in and they decide to get indoors. At Arthurs house, the boys play a game of pool, in which Dan forgets he's suppose to take his grandmother's dog for a walk.Six miles northeast of Blainsworth 4:30 p.m.; Dan arrives at his grandmother Goldie's house where his father is already there taking her dog to the vet, for it has a bad leg. Jack yells at Dan for not being responsible for anything, and Dan rides on his new bike home.Arthur arrives at the Hatch house, were Laura is getting ready to leave for work for the evening. Jenny arrives at the house to pick Laura up, were they talk about Jack being so domineering on Dan for he doesn't want Dan to end up a loser like him.Nightfall. Arthur and Dan play with musical instruments, while checking every few minutes if baby Ryan in the next room is all right. Jack then arrives and tells Dan and Arthur to bring their bicycles in for its raining. Going out, they find that its raining hard and the winds are picking up speed. Arthur tells Dan that since hes originally from Los Angeles, he enjoys the rain, while Dan sees little amusement in it, for he tells Arthur that rain and hailstorms can get bad.At the local diner in town, Laura is waitressing when Bob walks in asking for some coffee. Bob overhears a farmer named Gus talk about the storm and of tornados reported in the area. Bob tells Gus that most people killed by tornados 
 Question: Who is Danny infatuated with?

Ex Output:
arthur's sister stacey


Ex Input:
Context: Cystic fibrosis (CF) is the most common inherited disorder in Caucasian populations, with over 1400 mutations identified in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Mutations in the CFTR gene may be also causative for CBAVD (Congenital Bilateral Absence of the Vas Deferens). The type and distribution of mutations varies widely between different countries and/or ethnic groups, and is relatively unknown in Iran. We therefore performed a comprehensive analysis of the CFTR gene in Iranian CF patients. 69 Iranian CF patients, and 1 CBAVD patient, were analysed for mutations in the complete coding region, and its exon/intron junctions, of their CFTR genes, using different methods, such as ARMS (amplification refractory mutation system)-PCR, SSCP (single stranded conformation polymorphism) analysis, restriction enzyme digestion analysis, direct sequencing, and MLPA (Multiplex Ligation-mediated Probe Amplification). CFTR mutation analysis revealed the identification of 37 mutations in 69 Iranian CF patients. Overall, 81.9% (113/138) CFTR genes derived from Iranian CF patients could be characterized for a disease-causing mutation. The CBAVD patient was found to be homozygous for the p.W1145R mutation. The most common mutations were p.F508del (DeltaF508) (18.1%), c.2183_2184delAAinsG (2183AA>G) (6.5%), p.S466X (5.8%), p.N1303K (4.3%), c.2789+5G>A (4.3%), p.G542X (3.6%), c.3120+1G>A (3.6%), p.R334W (2.9%) and c.3130delA (2.9%). These 9 types of mutant CFTR genes totaled for 52% of all CFTR genes derived from the 69 Iranian CF patients. Eight mutations, c.406-8T>C, p.A566D, c.2576delA, c.2752-1_2756delGGTGGCinsTTG, p.T1036I, p.W1145R, c.3850-24G>A, c.1342-?_1524+?del, were found for the first time in this study. We identified 37 CFTR mutations in 69 well characterized Iranian CF patients, obtaining a CFTR mutation detection rate of 81.9%, the highest detection rate obtained in the Iranian population so far. These findings will assist in genetic counseling, prenatal diagnosis and future screening of CF in Iran. 
 Question: Which is the most common CFTR mutation in Caucasians?

Ex Output:

deltaf508