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 Input:
Robert is a fisherman who wants to find a way to catch more fish. He decided to try different sizes of hooks. Robert caught 4 catfish, 3 trout, and 7 perch while using worms for bait. Which is the independent (manipulated) variable in Robert's investigation?  
 (A) type of bait (B) size of hook (C) type of fish caught (D) number of fish caught

Ex Output:
B


Ex Input:
Biologists are studying the white-tailed deer population in Ohio. Which question could the biologists most likely answer?  
 (A) How fast does this deer population grow? (B) What percentage of people enjoy watching deer? (C) Does this deer population like warmer states? (D) Should people raise deer as pets?

Ex Output:
A


Ex Input:
The Earth and the Moon have all of these common features except  
 (A) core. (B) crust. (C) water. (D) mantle.

Ex Output:

C