_______ laws of motion are simple, motion, as we see it in the world about us, certainly is not. 
#34130
A
When
B
While
C
As
D
Even
推荐题目
________we went to visit Professor Smith, he________his research work.
#31550
A
The first time; devoted to
B
Whenever; was concentrate on
C
For the first time; was busy with
D
Each time; was absorbed in