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 tool would be best to use for counting the number of legs on an ant?  
 (A) ruler (B) hand lens (C) calculator (D) microscope

SOLUTION: B

PROBLEM: Which difference between water and ice results in ice floating on cold water?  
 (A) heat (B) shape (C) density (D) volume

SOLUTION: C

PROBLEM: Which explains how the epithelium offers protection to land-dwelling vertebrates?  
 (A) Epithelium provides a rigid shell to prevent punctures. (B) Epithelium has capillaries to resist iron deficiency. (C) Epithelium insulates the vertebrate from hypothermia. (D) Epithelium prevents dehydration in vertebrates.

SOLUTION:
D