instruction:
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.
question:
Scientists have studied the specific stages in the life cycle of stars. In which stage do stars spend most of their lifetime?  
 (A) red giant (B) black dwarf (C) white dwarf (D) main sequence
answer:
D


question:
Cell membranes allow some molecules to move freely across the membrane, while other molecules are restricted. Which term best describes this capability of a cell membrane?  
 (A) semipermeable (B) impervious (C) resilient (D) unyielding
answer:
A


question:
Maria Mitchell discovered a comet in 1847 that was later named after her. Maria Mitchell's discovery contributed to which branch of science?  
 (A) biology (B) chemistry (C) geology (D) astronomy
answer:

D