Is the example a complete sentence, sentence fragment, or run-on sentence?
to notice in what ways our old neighborhood has changed.
a. run-on sentence
b. complete sentence
c. sentence fragment

The correct answer is C. Sentence fragment. This is because the sentence is syntactically such that it has no clear meaning, which is why it requires a context or a creation of a newer, more complex sentence. An example would be if we transformed it into "It took us a while to notice in what ways our old neighborhood has changed" or something similar.

It would be