What is the simple subject in this sentence?

The Saturn rocket made travel to the moon possible.

A. moon

B. travel

C. Saturn

D. rocket

The answer is letter D.

Rocket is the simple subject in the sentence above. Simple subjects are the most basic units in sentence constructions. A subject is a noun that talks about a person, place, thing, or idea. It tells us what the sentence going to be about and without it we cannot have a complete sentence that has sense. In the sentence above, the rocket is the subject of the sentence which is responsible for the effect of making space travel possible.