TASK DEFINITION: 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.
PROBLEM: 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.

SOLUTION: A

PROBLEM: The excessive use of nitrogen-based fertilizers causes runoff that increases the nitrogen content of lakes and bays. These nitrogen compounds directly affect the aquatic ecosystems by  
 (A) interfering with the water cycle. (B) decreasing the predator population. (C) increasing the rate of algae growth. (D) causing aquatic animals to grow larger.

SOLUTION: C

PROBLEM: Which cellular structure do organisms in the kingdoms Eubacteria, Archaebacteria, and Protista have in common?  
 (A) a nucleus (B) a cell membrane (C) a circular chromosome (D) a mitochondrion

SOLUTION:
B