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.

[EX Q]: Which involves the greatest variety of cell types?  
 (A) a tissue (B) an organ (C) an organ system (D) an organism
[EX A]: D

[EX Q]: Which is a trait that a child can inherit from its parents?  
 (A) eye color (B) a broken leg (C) length of hair (D) language skills
[EX A]: A

[EX Q]: Diseases that can be transmitted between organisms are  
 (A) infectious. (B) inherited. (C) environmental. (D) congenital.
[EX A]:
A