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: Which of the following compounds is most likely to be part of living organisms?  
 (A) C?H??O? (B) BF? (C) MoCl? (D) CsI

SOLUTION: A

PROBLEM: Which of the following is most likely to disrupt the natural balance in an ecosystem?  
 (A) introduction of a non-native species (B) reduced daylight hours during winter (C) preventing the cutting of trees in forests (D) riverbank erosion resulting from springtime flooding

SOLUTION: A

PROBLEM: A student is conducting an investigation on static electricity. The student has three balloons and rubs two of them on a piece of wool. The student then touches each balloon to a wall to observe if static electricity would cause the balloon to stick. What is the independent variable in this investigation?  
 (A) the height of the wall (B) the number of balloons (C) the attraction to the wall (D) the rubbing action on the wool

SOLUTION:
D