He did everything he could （ ） away from it
问题描述：
He did everything he could （ ） away from it
这是一篇完形天空里的句子.
答案选项有：
A to keep
B keep
C to stop
D stop
我选的是B,我认为是could do sth,并且keep away from sth是远离某物的意思吧?应该不选to do结构的.而答案却选A.请您说明一下为什么?
（前文大意是：亨利*福特的爸爸是个农夫,他爸爸有个农场,希望亨利接管,但亨利对农场不感兴趣.）
答
he could是everything的后置定语
He did everything he could （to keep） away from it.
如果改成简单句应该是He did everything（to keep） away from it.
he could 跟这个句子无关