题目：
Volunteers provide vital extra
help,___ which the sanctuary staff would be unable to complete certain project
s.
a. for
b. by
c. without
d. from
答案是c.
以下是解析：
为
Volunteers provide vital extrap help.
和
The sanctuary staff would be unable to complete certain projects without extra
help.
的整合
我的疑惑：
请问这种把介系词移到which 前面的做法是等同于 for which那样子吗？
像是这个网址里面的做法一样：
https://www.7plus3english.com/in-which-for-which-on-which-at-which-%E7%9A%84%E
7%94%A8%E6%B3%95/
先谢谢各位的解惑！