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.

[EX Q]: 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.
[EX A]: B

[EX Q]: A student conducts an investigation. In order to make a valid conclusion, she must  
 (A) have a testable hypothesis. (B) place the data in a graph. (C) use the best technology. (D) test multiple variables.
[EX A]: A

[EX Q]: Decomposers increase the fertility of the soil and prevent dead organisms from building up in the environment. In which way do decomposers make the soil more fertile?  
 (A) by adding carbon (B) by adding nitrogen (C) by removing excess water (D) by removing excess minerals
[EX A]:
B