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]: Ella waves good-bye from the bus. What body system pulls on bones to let Ella wave her arm?  
 (A) muscular system (B) nervous system (C) digestive system (D) circulatory system
[EX A]: A

[EX Q]: The cells of a plant help the plant maintain its life functions. What part of a plant cell has the function of producing sugar in the presence of sunlight?  
 (A) chloroplast (B) cytoplasm (C) mitochondria (D) nucleus
[EX A]: A

[EX Q]: What is generated when the students count and record the number of organisms in the pond water?  
 (A) data (B) variables (C) a hypothesis (D) a conclusion
[EX A]:
A