When he was a boy, he used to go there and watch _____.
A. to repair bicycles
B. bicycles to be repaired
C. bicycles being repaired
D. repairing bicycles
When he was a boy, he used to go there and watch _____.
A. to repair bicycles
B. bicycles to be repaired
C. bicycles being repaired
D. repairing bicycles
C
用-ing形式一般式的被动语态作宾语补足语，强调自行车被修理的过程。