Someone had broken into Sam's house! Police came to investigate and a crime scene analyst collected evidence: broken glass, a piece of torn cloth, swabs from blood drops. Sam watched the crime scene analyst and thought he'd like to do that one day. It was a scientific way to solve puzzles! "You'd better get busy and study!" said his mother. "You know forensic scientists must have strong backgrounds in __________."
A) chemistry.
B) geology.
C) law.
D) mathematics.