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.

Example Input: In the 17th century, Galileo proposed a hypothesis to explain how suction pumps work. Galileo's hypothesis was disproved, but later it helped Torricelli in the development of an instrument for measuring atmospheric pressure. How did Galileo's hypothesis most likely help with the development of this new technology?  
 (A) by leading Galileo to design a different technology (B) by allowing another scientist to critique Galileo's hypothesis (C) by providing evidence of the effects of atmospheric pressure (D) by inspiring another scientist to test an alternative hypothesis
Example Output: D

Example Input: Two forms of boron are naturally occurring, boron-10 and boron-11. What difference exists between a boron atom with a 10 atomic mass units (amu) and a boron atom with 11 atomic mass units (amu)?  
 (A) amount of neutrons (B) number of electrons (C) size of protons and neutrons (D) size of electrons and electron cloud
Example Output: A

Example Input: A river erodes its banks for thousands of years, and deposits the eroded material at its mouth. What two landforms did the river make?  
 (A) a hill and a delta (B) a delta and a canyon (C) a canyon and a dune (D) a dune and a delta
Example Output:
B