图所示，用手拉橡皮筋，橡皮筋伸长。此时手的感觉是
A.手有力作用在橡皮筋上
B.橡皮筋具有弹性势能
C.橡皮筋对手有力的作用
D.橡皮筋因伸长而变细
答案：C
--- How many times have you been to China?
--- In fact, it is the first time that I ______ here.
A．was
B．am
C．had been
D．have been
简述漏电的原因？
