My little brother is too young to look after himself。用enough改为同义句

Question

MY little brother isn’t ____ _____ to look after himself。
初二的，注意 是两空。

Answer 1

MY little brother isn’t (old) (enough) to look after himself。
我弟弟太小还不能照顾自己。

Answer 2

much enough

Answer 3

old enough