Answer
Choice A.
Work Step by Step
Equation 11–11a tells us that the period of a pendulum is proportional to the square root of its length and inversely proportional to the square root of g, $T=2 \pi \sqrt{\frac{L}{g}}$. To speed up the pendulum and decrease the period of the oscillation, one can shorten the string.
The mass of the bob does not affect the period of the pendulum.