He was busy writing the exam paper , only ___once in a while to check the time.  
#94095
A
to stop
B
stopping
C
to have stopped
D
having stopped
推荐题目
Most of the teachers ______ to visit our school were young ones.
#95272
A
invited
B
to invite
C
being invited
D
had been invited
My father insisted that every minute _____made full use of ________the work well.
#90562
A
be,to do
B
has been,doing
C
be,doing
D
has been,to do
Food safety is one of the problems      now all over the world.
#91716
A
discussed
B
to be discussed
C
being discussed
D
having been discussed