What is the infinitive phrase in this sentence?

In August, we went to Ontario and to upstate New York to see Niagara Falls.
A. to Ontario
B. to upstate New York
C. to see
D. to see Niagara Falls

I think its C

That's an infinitive, but it's not an infinitive phrase.

So it would be D?

Yes. To see Niagara Falls is the infinitive phrase.

To determine the infinitive phrase in the given sentence, we need to identify the phrase that starts with the word "to."

In this sentence, there are two infinitive phrases: "to Ontario" and "to upstate New York." Since the question asks for the singular infinitive phrase, the correct answer is A. "to Ontario."

The infinitive phrase "to Ontario" functions as a prepositional phrase, indicating the destination of the trip. It follows the verb "went" and answers the question "where did we go?"

Thus, the correct answer is A. to Ontario.