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.

[EX Q]: Which of the following is the best observation of the refraction of light?  
 (A) Looking at oneself in a mirror (B) Looking at a shadow of an object (C) Viewing an object through an open window (D) Viewing an object partially in water
[EX A]: D

[EX Q]: Which of the following is the best example of potential energy?  
 (A) a fallen rock (B) a burning match (C) a liter of gasoline (D) a red-hot piece of iron
[EX A]: C

[EX Q]: Joyce is conducting a traffic survey and needs to find out how many cars cross the crosswalk in the morning before the school bell rings. How should she collect this data?  
 (A) Make a tally chart (B) Draw a pictograph (C) Take a picture of each passing car (D) Write down the cars' license plate numbers
[EX A]:
A