In this task, you're given an article, a question which often contains a blank and four options (associated with "A", "B", "C", "D"). Your task is to find the correct answer (from the given options) for the question from the given article and return one of the options from "A", "B", "C", and "D". Do not generate anything else apart from one of the following characters: "A", "B", "C", "D". There is only one correct answer for each question.

[EX Q]: Article: Winter begins in the north on December 22nd. People and animals have been doing what they always do to prepare for the colder months. Squirrels , for example, have been busy gathering nuts from trees. Well, scientists have been busy gathering information about what the squirrels do with the food they collect. They examined differences between red squirrels and gray squirrels in the American state of Indiana. The scientists wanted to know how these differences could affect the growth of black walnut trees. The black walnut is the nut of choice for both kinds of squirrels. The black walnut tree is also a central part of some hardwood forests. Rob Swihart of Purdue University did the study with Jake Goheen, a former Purdue student now at the University of New Mexico. The two researchers estimate that several times as many walnuts grow when gathered by gray squirrels as compared to red squirrels. Gray squirrels and red squirrels do not store nuts and seeds in the same way. Gray squirrels bury nuts one at a time in a number of places. But they seldom remember where they buried every nut. So some nuts remain in the ground. Conditions are right for them to develop and grow the following spring. Red squirrels, however, store large groups of nuts above ground. Professor Swihart calls " _ ". Gray squirrels are native to Indiana. But Professor Swihart says their numbers began to decrease as more forests were cut for agriculture. Red squirrels began to spread through the state during the past century. The researchers say red squirrels are native to forests that stay green all year, unlike walnut trees. They say the cleaning of forest land for agriculture has helped red squirrels invade Indiana. Jake Goheen calls them a sign of an environmental problem more than a cause.
Question: The study done by Rob Swihart and Jake Goheen is to _ .
Options: (A) find out the living conditions for squirrels (B) learn squirrels' influence on black walnut trees (C) do something to get rid of squirrels (D) save the forests in the American state of Indiana
[EX A]: B

[EX Q]: Article: By Road Around the World Nickname: Walker Email: ragwani@hotmail.com When to travel: May 2011-Aug 2011 Who am I: I am 55. From my childhood, have this dream to go around the world by hitch hiking. However this is now changed and I want to go by road. My travel plans: Going throughout the world and study various people, culture, habits. Who am I looking for: A female companion, and she must have similar interest as me. Just for fun Nickname: Stream Email: qrutta@yahoo.co.uk When to travel: Jan 2011-Dec 2011 Who am I: Young slim girl, looking to see Asia with anyone who wants to travel. My travel plans: I most prefer a white man in his late30's to have fun with me as he travels either on business or leisure trips Whom am I looking for: Someone who is honest, friendly; good sense of humor, adventurous. 22yr old Australian looking for travel companion Nickname: Angela Email: alyssia _ europe@hotmail.com When to travel: March 2011 Who am I: a lovely girl, with fun, honest, caring. My travel plans: I will be traveling to Europe cities, then the world! Who am I looking for: An extremely fun and entertaining male/female, middle-aged, someone that I can enjoy every travel moment with. Fun and maybe more Nickname: Sunnygirl Email: sunnygirl2008@yahoo.com When to travel: Jun2011-Aug2011 Who am I: Slender African girl in her late 20's. Quite charming, loving, pretty,fun to be with. My travel plans: Nothing in mind for sure, just looking to come with you. Whom am I looking for: Looking for a white male between 40-50 years, someone who is full of energy and lively.
Question: What way would Walker like to choose for his travel this time?
Options: (A) By plane. (B) By road. (C) By water. (D) By hitch hiking.
[EX A]: B

[EX Q]: Article: There are two kinds of changeschemical change and physical change. In a chemical change, there is always a new substance formed. Breaking up water into hydrogen and oxygen is a chemical change. In each of the chemical change at least one new substance is formed. A change is not a chemical change if it doesn't form a new substance. Physical changes are very common, too. There are many examples. You can make a physical change by tearing a piece of paper into two, or by cutting a piece of iron with lathe . Here paper is still paper, and the iron is still iron. Another way of making physical change is dissolving something in water. When you dissolve salt in water, the salt disappears. You may think that a new substance has been formed. But really there is no new substance. The salt is still salt. You can still taste it. So the dissolving of anything is a physical change. When water freezes, the change is also a physical one. The water changes from liquid to solid, but it is still the same substance. That is why the freezing of anything is a physical change.
Question: In a physical change _ .is formed.
Options: (A) a new substance (B) nothing new (C) a piece of paper (D) a piece of iron
[EX A]:
B