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.

Input: Consider 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

Output: B


Input: Consider Input: Some scientists predict that as greenhouse gases change the climate of Earth, the number and strength of hurricanes will increase. In order for this to occur, the climate change would have to affect Earth by changing the  
 (A) depths of the oceans. (B) speed of currents in the oceans. (C) chemical compositions of the oceans. (D) amount of dissolved oxygen in the oceans.

Output: B


Input: Consider Input: Which of these is not part of an atom?  
 (A) proton (B) isotope (C) nucleus (D) electron


Output: B