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: What property is the same for each atom of an element?  
 (A) energy (B) mass number (C) atomic number (D) number of neutrons

SOLUTION: C

PROBLEM: On a field trip, a student holds a frog and reports that it has slippery skin. This is an example of  
 (A) a measurement (B) a prediction (C) an explanation (D) an observation

SOLUTION: D

PROBLEM: Which group of organisms can show significant trait changes in the shortest period of time?  
 (A) bacteria (B) birds (C) fish (D) reptiles

SOLUTION:
A