__  carefully if any change occurs when doing experiments in the lab..
#88398
A
Observe
B
To observe
C
Observed
D
Observing
推荐题目
_____ to school this morning, I met a friend of mine.
#95824
A
I was walking
B
Walking
C
While I walking
D
Walked
He had to have the washing machine _________ last night.
#96133
A
to mend
B
mending
C
mended
D
being mended
The question          at tomorrow’s meeting will be of importance.
#97700
A
discussed
B
to be discussed
C
been discussed
D
being discussed