a little boy was drowning but that policeman dived in the river and saved him为什么是was drowning 、不是but 前后时态一致的么.何况小孩是在警察叔叔救他之前淹到的 还ing?

问题描述:

a little boy was drowning but that policeman dived in the river and saved him
为什么是was drowning 、不是but 前后时态一致的么.何况小孩是在警察叔叔救他之前淹到的 还ing?