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.

Which of the following climates has cold winters and hot summers?  
 (A) polar (B) subtropical (C) temperate (D) tropical
C

The changing appearances of the nighttime sky over the surface of Earth and eclipses of the Moon have provided evidence that  
 (A) Earth is a sphere. (B) Earth supports life. (C) Earth has a layered atmosphere. (D) Earth is covered mostly with water.
A

What is a job of white blood cells?  
 (A) transport oxygen (B) remove waste (C) fight disease (D) enable reproduction

C