Question

I remember them talking about_________futures, going to college, and starting over.*

Answer 1

I remember them talking about their futures, going to college, and starting over.

Theirs can be easily eliminated because it is not a word
They're means they are, which makes no sense
And There usually is pointing someone towards a location.

Meanwhile, their is possessive, and the subjects' futures belong to them. Hope I helped! ^__^

Answer 2

their is the answer:)
because (they're) is also a contraction for "they are" and thats not right
(there) is used to show direction
(theirs) is also not right because future already has an S for you:)
hope this helps 
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