[单选题]
A mass attached to the free end of a spring executes simple harmomaqwy.1 3rx3wiyub81 nic motion ac72gtip ox +xh( x3i/bmcording to the eqhmbx+27x 3( oti/pig xuation $y = 0.50 \; \sin (18\pi \times t)$ where y is in meters and t is seconds. What is the period of vibration?
A. $9.0 \; s$
B. $18 \; s$
C. $1/9 \; s$
D. $1/18 \; s$
