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:
A scientist makes a discovery while performing an investigation, but fails to maintain clear records of the tests performed. In which way does a lack of record keeping affect a scientist's work?  
 (A) It invalidates the procedures and conclusions. (B) It makes the data obtained in the study incorrect. (C) It prevents other scientists from validating the results. (D) It prohibits other scientists from developing new hypotheses.

Ex Output:
C


Ex Input:
Which body system's primary function is the continuation of the species?  
 (A) digestive (B) nervous (C) excretory (D) reproductive

Ex Output:
D


Ex Input:
The weight of heavy machinery compacts soil, especially when it is wet. Why do farmers avoid driving their machinery across wet ground?  
 (A) Compacted soil will absorb too much water. (B) Plants cannot grow when soil is compacted. (C) Minerals are destroyed when soil is compacted. (D) Compacted soil increases soil acidity.

Ex Output:

B