For the Simple Harmonic Motion Described by the Trigonometric Function,find $d = \frac { 1 } { 4 } \cos 20 \pi t$

Multiple Choice

For the simple harmonic motion described by the trigonometric function,find the maximum displacement.? $d = \frac { 1 } { 4 } \cos 20 \pi t$ ?

A) $\frac { 1 } { 20 }$ ?
B) $\frac { 20 } { 4 }$
C) $\frac { 1 } { 4 }$
D) $\frac { 4 } { 20 }$
E) $20$