There is a relationship between the number of hours a plumber works and the amount of money he earns. The plumber earns $60 for every 2 hours he works. Which statement about the relationship and the amount of money the plumber earns is true?

A.
The number of hours the plumber works is the dependent variable in the relationship, and he earns $270 for 9 hours of work.

B.
The number of hours the plumber works is the independent variable in the relationship, and he earns $270 for 9 hours of work.

C.
The amount of money the plumber earns is the dependent variable in the relationship, and he earns $540 for 9 hours of work.

D.
The amount of money the plumber earns is the independent variable in the relationship, and he earns $540 for 9 hours of work