________ on ten years of observation and study, Professor Wang announced that everyone dreams every night，whether they realize it or not.
#88276
A
Basing
B
Based
C
Been based
D
Having based
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________ many times，I still didn't know how to operate the machine.
#91844
A
Having taught
B
Having been taught
C
Being taught
D
Teaching
Mike failed to finish his homework on time, so he tried to avoid _______ his teacher.
#96467
A
meet
B
to meet
C
to meeting
D
meeting
I’m tired out．I stayed up the whole night, ______ for my midterm math exam．
#95982
A
studying
B
to study
C
to be studying
D
studied