Which sentence contains a prepositional phrase?
a. running all the way, he got there early.
b. with the proper , they'll complete the project early.
(c. they tried, although they didn't expect to win.) i know is wrong
d. they sang it, then sang it again.

The question is asking us to chose which sentence contains a prepositional phrase". A propositional phrase contains (typically starts with) a preposition, and the only preposition in the following sentence is "with" (some other prepositions are "in" and "of"). So the correct answer is B. With the proper help, they'll complete the project early.

The sentence that contains a prepositional phrase is B. With the proper help, they'll complete the project early. A prepositional phrase obviously starts with a preposition. There are no prepositions in the other sentences, so B has to be the correct answer. The phrase "with the proper help" starts with the preposition with, and is thus the correct answer.