__ 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
After ________in the research for so many years，the scientist succeeded in finding the result at last.
#93113
A
buried
B
being buried
C
having buried
D
having been buried
More highways have been built in China, ______ it much easier for people to travel from one place to another.
#90583
A
having made
B
made
C
to make
D
making
_________ in a heavy rain，Robert fell ill and couldn’t help but _________ for a leave.
#91535
A
Caught; to ask
B
Catching; ask
C
Catching; to ask
D
Caught; ask
________ an effective team member, you need to develop a teamwork attitude.
#90793
A
Become
B
Becoming
C
Having become
D
To become
________by a group of children，the old man was delighted.
#94521
A
To be surrounded
B
Surrounding
C
Surrounded
D
To be surrounding