parents will always be there and give everythingthey could to make you happy这句话为什么要在could后加to?不加不是也对吗?

parents will always be there and give everything （they could） to make you happy
they could 是修饰everything

they could是everything 作先行词的定从，省略了连词。而这个to不是make的动词不定式，是表目的的。parents will always be there and give everything.The thing that（或其它连词）they could. The do them to make you happy.这样把句子分开，意思不变，但更易理解了，希望可以帮助到您。

parents will always be there and give everything (they could) to make you happy
括号内为定语从句,修饰everything，而to make you happy为不定式作目的状语的用法，表示“为了让你高兴”，所以could to不是连在一起的，请小心。
祝学习愉快，望采纳，谢谢！

could 后面怎么可能加to呢？而且也没有省略什么成分啊

parents will always be there and give everything (they could) to make you happy 括号内为定语从句,修饰everything,而to make you happy为不定式作目的状语的用法,表示“为了让你高兴”,所以could to不是连在一...

could 和to 并不连用


parents will always be there and give everything they could， to make you happy

这样断句，你就明白了。