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]: Which illness is always caused by an infection?  
 (A) a heart attack (B) a broken bone (C) influenza (D) cancer
[A]: C


[Q]: When iron combines with oxygen in a moist environment, rust forms because of a  
 (A) chemical reaction. (B) physical reaction. (C) change in density. (D) change in temperature.
[A]: A


[Q]: A researcher is working on a family genetics project. She wants to trace a particular trait back through several generations of her ancestors. Which type of display will best help the researcher organize the information?  
 (A) flow chart (B) cycle diagram (C) pedigree chart (D) Punnett square
[A]:
C