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.

[Q]: Which of the following was invented by Benjamin Franklin?  
 (A) bifocal lens (B) telescope lens (C) telephone (D) camera
[A]: A


[Q]: Melting, boiling, and freezing are examples of  
 (A) physical changes. (B) chemical changes. (C) magnetic changes. (D) electrical changes.
[A]: A


[Q]: What is the smallest unit of a chemical compound that still has the properties of that compound?  
 (A) a nucleus (B) a molecule (C) an element (D) an atom
[A]:
B