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.

[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.
[A]: A


[Q]: Which substance do all living things require to survive?  
 (A) blood (B) water (C) carbon dioxide (D) organic soil
[A]: B


[Q]: Which life function is the same for an amoeba as for other freshwater protists?  
 (A) the method used to obtain nutrients and energy (B) the process used to constantly remove excess water (C) the method used to detect changes in their environment (D) the process used to remove waste products from their cytoplasm
[A]:
B