Read the sentence.

What the teacher said surprised us all.

The bolded words are what kind of clause?

1. noun clause 2. adverb clause 3. adjective clause

I believe that the bolded part is "What the teacher said," but if not the answer will still be below. In the case that I am correct it is a Noun clause, because "what the teacher said" functions as a noun in the sentence.

Otherwise, if "surprised us all" or just "surprised us" is the bolded part, I am confident that this is an elliptical clause, which would mean it is a dependent adverb clause.