他只能打给他的律师。the only thing he could do is to call h

他只能打给他的律师。the only thing he could do is to call h

is/ was 后面的动词形式由is/ was前面的具体动词来决定.再看以下例句
the only thing he did was (to) call his wife
the only thing he could do was call his wife
the only thing he wanted to do was to call his wife
the only thing he enjoyed doing was calling his wife
所以这里to call 是错的，应该是the only thing he could do is call his lawyer

这是系表结构。
is 后面是一件事情
to表示目的。
to后面的部分是对thing的解释说明。
the only thing =to call his lawer
这是名词性的。用is+名词性。