题目2单选题
我国的电网频率<img src="https://tihai-oss-cloud.itihey.com/img/719635e1c9f94ea71c295584c91e6e8a.png">为( )A. <img src="https://tihai-oss-cloud.itihey.com/img/84a7da99203060bb6a43432e6ee72ced.png">B. <img src="https://tihai-oss-cloud.itihey.com/img/76d2d14a407d9568d0e4f633c273c402.png">C. <img src="https://tihai-oss-cloud.itihey.com/img/0c446fdd658f5f9a0edd9cf00eee093c.png">D. <img src="https://tihai-oss-cloud.itihey.com/img/9b2f0929cf46077f6db72b150ef862cc.png">