At the minimum, a prepositional phrase will begin with a preposition and end with a noun, pronoun, gerund, or clause, the "object" of the preposition. In = preposition; the, weedy, overgrown = modifiers; garden = noun.
They deserve to live no matter what. It wouldn’t be fair for them. If humans were like animal’s and animals were like humans we would see how they would die. Slowly and painfully. It’s not fair for them
B is the most realistic answer considering Amerigo's objective: to provide the students with one-on-one Italian instruction. The rest of them are not one-on-one and are pretty unnecessary.
I hope I helped!