TASK DEFINITION: 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.
PROBLEM: Context: The photo above represents water in three common states of matter. States of matter are different phases in which any given type of matter can exist. There are actually four well-known states of matter: solid, liquid, gas, and plasma. Plasma isnt represented in the iceberg photo, but the other three states of matter are. The iceberg itself consists of water in the solid state, and the lake consists of water in the liquid state. Q: Where is water in the gaseous state in the above photo? A: You cant see the gaseous water, but its there. It exists as water vapor in the air. Q: Water is one of the few substances that commonly exist on Earth in more than one state. Many other substances typically exist only in the solid, liquid, or gaseous state. Can you think of examples of matter that usually exists in just one of these three states? A: Just look around you and you will see many examples of matter that usually exists in the solid state. They include soil, rock, wood, metal, glass, and plastic. Examples of matter that usually exist in the liquid state include cooking oil, gasoline, and mercury, which is the only metal that commonly exists as a liquid. Examples of matter that usually exists in the gaseous state include oxygen and nitrogen, which are the chief gases in Earths atmosphere. A given kind of matter has the same chemical makeup and the same chemical properties regardless of its state. Thats because state of matter is a physical property. As a result, when matter changes state, it doesnt become a different kind of substance. For example, water is still water whether it exists as ice, liquid water, or water vapor. The most common states of matter on Earth are solids, liquids, and gases. How do these states of matter differ? Their properties are contrasted in the Figure 1.1. Click image to the left or use the URL below. URL: Properties of matter in different states. Q: The Figure 1.2 shows that a liquid takes the shape of its container. How could you demonstrate this? A: You could put the same volume of liquid in containers with different shapes. This is illustrated below with a beaker (left) and a graduated cylinder (right). The shape of the liquid in the beaker is short and wide like the beaker, while the shape of the liquid in the graduated cylinder is tall and narrow like that container, but each container holds the same volume of liquid. Q: How could you show that a gas spreads out to take the volume as well as the shape of its container? A: You could pump air into a bicycle tire. The tire would become firm all over as air molecules spread out to take the shape of the tire and also to occupy the entire volume of the tire. 
 Question: the only state in which matter has a fixed shape is

SOLUTION: solid.

PROBLEM: Context: The authors describe a family with six patients with muscular dystrophy with a variable course. One is a compound heterozygote for CAPN3 mutations (calpainopathy) and the others have a single CAPN3 mutation. Linkage analysis and sequencing revealed a XK gene mutation (McLeod syndrome). This illustrates the variable phenotype of XK mutations and suggests the possibility that CAPN3 heterozygotes may have their condition caused by nonallelic mutations in other unrelated genes. 
 Question: Mutation of which gene is associated with McLeod syndrome?

SOLUTION: xk

PROBLEM: Context: Thermohaline circulation drives deep ocean circulation. Thermo means heat and haline refers to salinity. Dif- ferences in temperature and in salinity change the density of seawater. So thermohaline circulation is the result of density differences in water masses because of their different temperature and salinity. What is the temperature and salinity of very dense water? Lower temperature and higher salinity yield the densest water. When a volume of water is cooled, the molecules move less vigorously, so same number of molecules takes up less space and the water is denser. If salt is added to a volume of water, there are more molecules in the same volume, so the water is denser. Changes in temperature and salinity of seawater take place at the surface. Water becomes dense near the poles. Cold polar air cools the water and lowers its temperature, increasing its salinity. Fresh water freezes out of seawater to become sea ice, which also increases the salinity of the remaining water. This very cold, very saline water is very dense and sinks. This sinking is called downwelling. This video lecture discusses the vertical distribution of life in the oceans. Seawater density creates currents, which provide different habitats for different creatures: Click image to the left or use the URL below. URL: Two things then happen. The dense water pushes deeper water out of its way and that water moves along the bottom of the ocean. This deep water mixes with less dense water as it flows. Surface currents move water into the space vacated at the surface where the dense water sank (Figure 1.1). Water also sinks into the deep ocean off of Antarctica. Cold water (blue lines) sinks in the North Atlantic, flows along the bottom of the ocean and upwells in the Pacific or Indian. The water then travels in surface currents (red lines) back to the North Atlantic. Deep water also forms off of Antarctica. Since unlimited amounts of water cannot sink to the bottom of the ocean, water must rise from the deep ocean to the surface somewhere. This process is called upwelling (Figure 1.2). Upwelling forces denser water from below to take the place of less dense water at the surface that is pushed away by the wind. Generally, upwelling occurs along the coast when wind blows water strongly away from the shore. This leaves a void that is filled by deep water that rises to the surface. Upwelling is extremely important where it occurs. During its time on the bottom, the cold deep water has collected nutrients that have fallen down through the water column. Upwelling brings those nutrients to the surface. Those nutrients support the growth of plankton and form the base of a rich ecosystem. California, South America, South Africa, and the Arabian Sea all benefit from offshore upwelling. Upwelling also takes place along the Equator between the North and South Equatorial Currents. Winds blow the surface water north and south of the Equator, so deep water undergoes upwelling. The nutrients rise to the surface and support a great deal of life in the equatorial oceans. Click image to the left or use the URL below. URL: 
 Question: what helps to bring cool, nutrient-rich water to the surface?

SOLUTION:
upwelling