【单选题】
正弦波振荡电路如图所示,其振荡频率为()<br /> <img src="https://nimg.ppkao.com/2019-05/wangjiahui/201905151619183691.jpg?sign=490094d1d248e18cd286a0293769740b&t=62d68c14" /><br /> <img src="https://nimg.ppkao.com/2019-05/wangjiahui/2019051516193185870.jpg?sign=ea71ed08a306d6dcc6b4ad7592d64fb9&t=62d68c14" />
A、A
B、B
C、C