The equation of a plane progressive wave is given by
`y=2sin(100pit-(pix)/(20))`
where x and y are in cm and t is in second. The amplitude and the initial phase of the wave are respectively.
A. 2 cm and zero-radian
B. 1 cm and `pi`-radian
C. 2 cm and `pi`-radian
D. 2 cm and `(pi)/(2)` radian
