TASK DEFINITION: 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.
PROBLEM: Which particle type can be identified as being from a specific element?  
 (A) electron (B) atom (C) neutron (D) proton

SOLUTION: B

PROBLEM: Which of these is the center of our solar system?  
 (A) Mars (B) The moon (C) Jupiter (D) The sun

SOLUTION: D

PROBLEM: Which effect would the growing of legume crops such as beans and soybeans have?  
 (A) increase the efficiency of photosynthesis (B) greater immunity of crops against diseases (C) fewer bacteria in soil and in living organisms (D) more usable nitrogen for other plants

SOLUTION:
D