Instructions: 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.
Input: Which characteristic of a cell membrane allows it to control materials entering and leaving a cell?
(A) A cell membrane is surrounded by fluid. (B) A cell membrane is semipermeable. (C) A cell membrane holds organelles in place. (D) A cell membrane is found in plant and animal cells.
Output:
B