The children insisted---there on footA they going b they would go c on their going d going

问题描述:

The children insisted---there on foot
A they going b they would go c on their going d going

d going
The children insisted going there on foot

c
insist on doing是固定搭配 意思是坚持做某事

c
因为insist on 是固定搭配,后接动名词,这里是动名词的复合结构

D. insist doing sth. 坚持做。。。 固定搭配
或者:the children insisted on going...
the children insisted that they (should) go ...