The plan for the new design occurred to Mr. Smith______on his work recently.
#95059
A
while concentrated
B
while concentrating
C
while he concentrated
D
while concentrating himself
推荐题目
The horse _______ fur is red ______ to my nephew..
#93693
A
which; belong
B
who; belong
C
whose; belongs
D
that; belongs
She was afraid _____ the dog in case it became dangerous . 
#95142
A
of exciting
B
to excite
C
that she excited
D
to be exciting
____some doubt among scientists about the cause of cancer.
#92930
A
It exists
B
There exists
C
There is existing
D
It is existing