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.

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

Sal is looking at a map of Massachusetts. He has measured the distance, in inches, from Boston to Salem on the map. He wants to know how many actual miles the inches represent. What feature of the map should he look for?  
 (A) key (B) scale (C) legend (D) compass
B

The function of a plant's roots is to take in  
 (A) light and water (B) light and air (C) nutrients and water (D) nutrients and soil

C