[单选题]
An object in simple harmonicz+p d 9yb/f/(dupzt -v motion obeys the following positi-:0aytmd oz :uon versus time equat0z:-d au ymot:ion: $y = 0.50 \; \sin (\pi/2 \times t)$. What is the period of vibration?
A. $1.0 \; s$
B. $2.0 \; s$
C. $3.0 \; s$
D. $4.0 \; s$
