I have no choice but to give up.这一句型里but to give up做什么成分?

ut：prep。（介词）,后面的不定式是介词宾语,介词和介词宾语一起构成介词短语,在句中表选择,作状语例句：He wanted nothing but to stay here for another day。他只是想在这再呆一天。I have no choice but to tell you the truth。我只有告诉你实话。There was nothing to do but (to) wait till help came。只有等待救援了。* 如果谓语动词为实意动词do的某种形式时,but 后的不定式要省略符号to。如：I can do nothing but let him know。我只能通知她。They did nothing but complain。他们只是抱怨。