A student makes a hypothesis that the period of a pendulum depends upon the hanging weight

A student makes a hypothesis that the period of a pendulum depends upon the hanging weight. The student is provided with string attached to the ceiling, several masses, a ruler, and a stopwatch. The student sets up the pendulum and starts its motion, measuring the time for 10 full cycles.

What should be the independent and dependent variables to correctly test the hypothesis?

A. Independent: time; Dependent: mass

B. Independent: mass; Dependent: length of string

C. Independent: time; Dependent: length of string

D. Independent: mass; Dependent: time