串联型晶体振荡器是一种工作于石英谐振器的串联谐振频率上的振荡器,它把晶体作为一个具有高选择性的短路元件来使用。
参考答案:对
____ he ____ football two days ago?[ ]
A. Does, play
B. Did, played
C. Did, play
— Where is your brother, Lucy?
— He is busy _____ a kite. [ ]
A. make
B. makes
C. to make
D. making