You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. 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.

[Q]: Which substance do all living things require to survive?  
 (A) blood (B) water (C) carbon dioxide (D) organic soil
[A]: B


[Q]: Which physical structure would best help a bear to survive a winter in New York State?  
 (A) big ears (B) black nose (C) thick fur (D) brown eyes
[A]: C


[Q]: When a boy stands in a field in the sunlight, he usually is able to see his  
 (A) weight (B) temperature (C) reflection (D) shadow
[A]:
D