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: After a star runs out of most of its hydrogen fuel, it becomes hotter and more luminous. What stage does this represent in the life cycle of a star?  
 (A) quasar (B) protostar (C) red giant (D) white dwarf

Answer: C


Question: Which illustrates the correct order of relationships in organisms?  
 (A) tissue -> organ system -> organ -> cell (B) organ -> cell -> organ system -> tissue (C) cell -> tissue -> organ -> organ system (D) organ system -> organ -> cell -> tissue

Answer: C


Question: What is the primary function of skin cells?   
 (A) to deliver messages to the brain (B) to generate movement of muscles (C) to provide a physical barrier to the body (D) to produce carbohydrates for energy

Answer:
C