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.

Input: Consider 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

Output: D


Input: Consider Input: During which season of the year would a rabbit's fur be thickest?  
 (A) fall (B) spring (C) summer (D) winter

Output: D


Input: Consider Input: Which of the following travels from neuron to neuron as information is transmitted?  
 (A) electrochemical impulses (B) RNA strands (C) transport vesicles high in ATP (D) mechanical forces


Output: A