同義句轉換 Because they are not old enought,the students can't so

題目：

同義句轉換
Because they are not old enought,the students can't solve these kinds of problems all by themselves
Because they are ___ ___ ___ ___ these kinds of probiems all by themselves.

解答：

too young to solve
too ...to ...結構表示"太...而不能..."