​A noun clause functions as a noun or direct object

I didn't know that ​he wrote this book

​In short answers, SO replaces the noun clause

A: Does Mario Mendoza have a new book out?

​

​B: I think that Mario Mendoza has a new book out.

​ OR

​ I think so.

An adjective can also be followed by a noun clause

​I'm surprised that she hasn't written a new novel yet