定语从句什么时候必须用that什么时候不能用?
问题描述：
定语从句什么时候必须用that什么时候不能用?
答
1)先行词是不定代词：all,few,little,much,something,nothing,anything等.All that we have to do is to practise every day.2)先行词被序数词或形容词*所修饰.The first lesson that I learned will never be ...