You are given a science question (hard-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.

A scientist uses a special chemical marker to label some amino acids. He follows the marker until it becomes part of a large molecule in a cell. Which molecule does he find the chemical marker on?
(A) a lipid in a membrane (B) an enzyme in a lysosome (C) a polysaccharide in a cell wall (D) a DNA molecule in a mitochondrion
B