All of the plants now raised on farms have been developed from plants___wild.

问题描述:

All of the plants now raised on farms have been developed from plants___wild.
A.once they grew B.they grew once C.that once grew D.once grew答案选什么?为什么?

选C
农村上现在种植的植物都是从原先的野生植物发展而来.
once是曾经,原来的意思