The answer that makes the most sense is: “their”
Explanation:
Both Suzy and Beth will try to see “their” parents over the weekend.
The word their primarily works as a possessive adjective, to describe something that belongs to more than one person. A noun typically follows the word their.
Examples:
1) We walked “their” dog for them while they were on vacation.
2) Their cars were parked on the street while they were having “their” driveway repaved.
3) I offered to babysit “their” toddler, so they could go out on a date.
