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:
Rock layers with sand-sized particles were most likely deposited by  
 (A) wind. (B) water. (C) glaciers. (D) landslides.
answer:
A


question:
What are produced in both the male and female reproductive systems in humans?  
 (A) sperm (B) nutrients (C) fertilized eggs (D) sex cells
answer:
D


question:
What is one difference between birds and reptiles?  
 (A) Birds lay eggs and reptiles do not. (B) Reptiles are meat-eaters and birds are not. (C) Birds breathe oxygen and reptiles do not. (D) Reptiles are cold-blooded and birds are not.
answer:

D