EXERCISE 14–4 Using coordination and subordination
Example:

Arnold is a lifeguard in the summer. He teaches swimming during the school year. [Use subordination.]

Arnold, a lifeguard in the summer, teaches swimming during the school year.

Arnold is a lifeguard in the summer and teaches swimming during the school year.

The first sentence has a subordinate phrase, a lifeguard in the summer. The second sentence does not use subordination.