What is the simple subject in the following sentence? The space shuttle service have made travel to the international space station convenient and possible. A. travel B. possiible C. station D. shuttles

I am not the best at this but my guess would have to be C.

A subject is a noun which is a person, place, thing, or idea. A subject tells us who or what the sentence is going to be about.

The answer should be The Space Shuttle Service. I'm going to say to go with answer D. because the shuttles are the thing doing something in the sentence. What are they doing? Making it convenient to travel to the international space center.