You are given a science question (hard-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.

[EX Q]: A student performed this experiment: Four different types of seeds were planted in identical pots filled with the same kind and amount of soil. The pots were placed in a warm, sunny place and were given the same amount of water each day for a month. Which question about these seeds could be answered at the end of the month?  
 (A) Which seeds grew well in the dark? (B) Which seeds produced the tallest plants? (C) Which seeds survived in cold temperatures? (D) Which seeds needed the least amount of water?
[EX A]: B

[EX Q]: Students are designing kites to discover what type of kite flies the highest. Which is the most important to consider when designing a kite to fly high?  
 (A) string length (B) surface area (C) materials used (D) time of day
[EX A]: B

[EX Q]: Which of the following is a valid food chain?  
 (A) water -> grass -> fox -> hawk (B) sun -> rabbit -> moose -> wolf (C) grass -> spider -> mouse -> rabbit (D) dead mouse -> flies -> frog -> snake
[EX A]:
D