这个句子that从句用has to grow是正确的，用have to grow反而是错误的。你觉得既然强调句型强调的是主语you, that 从句的谓语动词就应该与you一致。这种理解是错误的。因为that 从句是个关系分句，但that的先行词并不是修饰，而是 it 。本句中 it = the person. 所以that的先行词实际是the person。很多人对强调句型有一种误解，以为只要把 It is ... that... 套在一个句子上，就是强调句型了，这种理解就会导致语法错误。假设你犯了错误却没有意识到，以为是别人犯了错误。现在我指出犯错误的是你，不是别人。句子的逻辑是 The person that/who has made a mistake is you. = It is you that/who has made a mistake. 强调句型的it在语法上是单数形式，所以主句总是用单数 It is/was...that..., 但it 提示的人或事物可能是单数也可能是复数，所以that从句的谓语动词的数由it表示的人或事物的数决定。如果it表示的是二个或以上的听话人，则that从句用复数谓语。例如 It is you that have to stop help each other. 如果听话人只有一个人，则that从句要用单数谓语动词。以下为COCA例句，that从句均用单数谓语动词。
The slightest hesitation and it will be you that is dead.
Though you set out to help other people, it will be you that becomes a much better person.
It was you that was burned up and strewn about.
It's you that has to change.
Because I'm fine with them. It's you that has the weird issues.
If I give you my wallet, it's you that has the power over me.
With all due respect Ken, it is you that has a lot to learn.
Since you decided to slander my name in your posts, it was you that was inviting a response from me.
I will give you some questions to look at, but it is you that does the work and I can only help.
Perhaps it is you that does not understand.
