【单选题】
一平面余弦波在t=0时刻的波形曲线如图所示,则O点的振动初相为:()<br /> <img src="https://nimg.ppkao.com/2018-09/wangjing/2018092716555332451.jpg?sign=62d99d38d690b72df8a2dd383e880973&t=62d1a722" /><br /> <img src="https://nimg.ppkao.com/2018-09/wangjing/2018092716560464071.jpg?sign=2ec068924d02e26704bdd6cab9e43bc2&t=62d1a722" />
A、A
B、B
C、C
D、D