Hello...What is the direct object in the following sentence? We were waiting in line for three hour?

I am pretty struggle with that. I have to pick one of those..





answers is line, waiting, hour, or no direct object in that sentence.Hello...What is the direct object in the following sentence? We were waiting in line for three hour?
It is not line because line is in a prepositional phrase. Hour is also in a prepositional phrase. It would either be waiting or no direct object.