在电路中，电源的突然接通或断开，电源瞬时值的突然跳变，某一元件的突然接入或被移去等，统称为（）。
参考答案：换路
In spite of these unexpected difficulties, the Chinese scientists ________ to carry out their experiments
on the lonely island. [ ]
A. threatened
B. managed
C. offered
D. hesitated
丝网印刷
