From The Tragedy of Macbeth by William Shakespeare

Prithee, see there!
Behold! Look! Lo! How say you?
Why, what care I? If thou canst nod, speak too.

Which highlighted group of words in this passage from The Tragedy of Macbeth by William Shakespeare is an adverb clause?

The highlighted group of words in this passage that is an adverb clause is "if thou canst nod."