Question

what meaning makes sense in the blank?
my cousins always feed treats to puppy.
they are
in that place
belongs to them

Explanation:

The sentence needs a possessive form to show the puppy belongs to the cousins. "they are" (they're) is a contraction for "they are" which doesn't fit. "in that place" (there) is an adverb. "belongs to them" (their) is the correct possessive form.

Answer:

belongs to them