[单选题]
A mass attached to thih+ ta6dj,pi4e free end of a spring executes * ray3: g:tjrksimple harmonic motion according to the :akrt*rg3: jy equation $y = 0.50 \; \sin (18\pi \times t)$ 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. $1/18 \; s$
