I him in time, otherwise he would have fallen off the bike.
A. had supported
B. supported
C. have supported
D. support
网友回答
A. had supported
(答案→)B. supported
C. have supported
D. support
解析：B 考察虚拟语气。句义：我及时扶住了他，要不然他就会从自行车上摔下来。根据题干中的otherwise he would have fallen off the bike可数是对过去事实进行虚拟，所以使用一般过去时。故B正确。