A swinging pendulum is constructed from a piece of string with a weight attached to the bottom. The length of the pendulum depends on how much string is let out. Suppose $L = f(t)$ is the length, in centimeters, of the pendulum at time $t$ minutes, and $P(L)$ is the period, in seconds, of a pendulum of length $L$.

Which of the following statements best explains the meaning of the composite function $P(f(t))$?