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 Input:
To calculate the relative age of rocks, geologists use the rate of radioactive decay of isotopes present in their samples. What is the term used for the original amount of the elemental isotopes being investigated?   
 (A) rare earth isotopes (B) son isotopes (C) daughter isotopes (D) parent isotopes

Ex Output:
D


Ex Input:
Which best describes a scientific theory?  
 (A) It is still being tested. (B) It is true, once written. (C) It is different for each continent. (D) It is determined in a court of law.

Ex Output:
A


Ex Input:
The temperatures in space vary from extremely cold to extremely hot. Earth's surface temperature is relatively stable. Which of these is most responsible for Earth's surface temperatures?  
 (A) solar radiation reflected from the Moon (B) many volcanic eruptions near the Ring of Fire (C) the greenhouse effect in the atmosphere (D) plankton distribution in shallow ocean waters

Ex Output:

C