直导体相对于磁场运动而切割磁力线时，在导体中将产生感应电动势。当导体运动方向和磁力线平行时，导体两端的感应电动势为______。
参考答案：零
选用in, on, from, for, to填空。
A. Hi, Dick! Where are you ?
B. Happy birthday you.
C. What's this English?
D. Where's my book? the bed.
E. This is an orange. It's you.
She couldn't help, even though she tried not to,（）at the strange clothes her friend was wearing.
A. to laugh
B. laugh
C. laughing
D. laughed
