The two sentences that use a noun clause are:
-
Emily spent several days thinking about what she had to do in order to make a good grade.
-
Why they didn’t return any of my phone calls or emails is the question I want answered.
In the first sentence, "what she had to do in order to make a good grade" is a noun clause functioning as the object of the preposition "about." In the second sentence, "Why they didn’t return any of my phone calls or emails" acts as the subject of the sentence.