The sentences with prepositional phrases are:
1. Using binoculars, we could see some of the features on the surface of the moon. The correct option is Sentence B
2. We will wait until the prices go down to buy smoked salmon. The correct option is Sentence A
3. The Fault in Our Stars, a novel by John Green, was made into a movie in 2014. The correct option is Sentence A
4. For most otters, fish is the main food, but they often supplement the fish with frogs, crayfish, and crabs. The correct option is Sentence A.
The Breakdown
1. The underlined part in sentence B, "Using binoculars," is a prepositional phrase. The preposition is "Using," and the object of the preposition is "binoculars."
2. The underlined part in sentence A, "until the prices go down," is a prepositional phrase. The preposition is "until," and the object of the preposition is "the prices go down."
3. The underlined part in sentence A, "a novel by John Green," is a prepositional phrase. The preposition is "by," and the object of the preposition is "John Green."
4. The underlined part in sentence A, "For most otters," is a prepositional phrase. The preposition is "For," and the object of the preposition is "most otters."