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:
Which statement explains why a mother's unhealthy diet during pregnancy is harmful to her embryo's development?  
 (A) The embryo inherits half its chromosomes from its mother. (B) The embryo receives its food from its mother through the placenta. (C) The embryo receives oxygen through the placenta. (D) The embryo receives mutations carried by its mother.
answer:
B


question:
What gas in the air do we need to breathe in order to live?  
 (A) nitrogen (B) oxygen (C) carbon dioxide (D) hydrogen (E) water vapor
answer:
B


question:
The skin, lungs, and kidneys work together to  
 (A) help eliminate body wastes. (B) help blood circulate. (C) aid in digestion. (D) aid in respiration.
answer:

A