thespeakercouldhardlyfindsafeground＿hisargument.A:onwhichtobas...thespeakercouldhardlyfindsafeground＿hisargument.A:onwhichtobaseB:tobaseonC:whichtobaseon选哪个,答案说是定语从句,但是后面怎么能还

Question

the speaker could hardly find safe ground ＿his argument .A:on which to bas...
the speaker could hardly find safe ground ＿his argument .A:on which to base B:to base on C:which to base on 选哪个,答案说是定语从句,但是后面怎么能还原成一个句子啊?

Answer 1

选择A
还原 1 the speaker could hardly find safe ground
2 he bases his arguement on the ground.
不过这里用的是类似where+to do 不定式作定语,而不是定语从句.即
the speaker could hardly find safe ground where to base his arguement. (on which=where)