Brandon is working on a speech about entering local running races. Examine his outline.

1. Running elevates the heart rate and is an effective way to support your metabolism.

2. Entering a race encourages runners to keep training.

3. Races help build a sense of community among people who live a healthy lifestyle.

Which source should he BEST use to research supporting facts for his first point?

A.
An article by a runner
B.
A book about running techniques
C.
A 2003 book authored by a scientist
D.
A 2013 article found on a medical search engine