What is a group of words that begins with a preposition and ends with an object?

a. prepositional phrase
b. adverbial phrase
c. prepositional relationship
d. dependent clause

answer is a. prepositional phrase

a prepositional phrase begins with a preposition and ends with its object.

Prepositional phrase

Explanation: Prepositional phrases always start with a preposition and always end with a noun or a pronoun called the object of the preposition.

Let's look at an example.

A vase of flowers fell on the floor.

We have two prepositional phrases in this sentence. "Of flowers" would be one because "of" is a preposition and "flowers" is the object.

"On the floor" would be another prepositional phrase because "on" is a preposition and "floor" is the noun that it works with.  

the apollo program, also known as project apollo, was the third united states human spaceflight program carried out by the national aeronautics and space administration (nasa), which succeeded in landing the first humans on the moon from 1969 to 1972.