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.

Example Input: A student plans to grow algal colonies in solutions with different concentrations of liquid fertilizer. Which is a clear and testable hypothesis to guide this investigation?  
 (A) Algae like fertilizer. (B) Fertilizer is good for algae. (C) Fertilizer improves the genetic traits of algae. (D) Algal growth rate increases with fertilizer concentration.
Example Output: D

Example Input: In animal skin tissue, cell division is responsible for  
 (A) growth and repair (B) sexual reproduction (C) obtaining energy (D) production of sex cells
Example Output: A

Example Input: Needles on a cactus plant are actually leaves. This needle shape helps the plant survive by  
 (A) catching food. (B) preventing water loss. (C) staying in place. (D) reproducing.
Example Output:
B