Third person plural pronoun is THEY.
If you want to create a possessive pronoun out of that one, that would be THEIRS.
Possessive pronouns, as the name itself says, determine some kind of possession. For example:
Is this books yours? - No, it's theirs.
You can recognize this spider by its white stripe markings on its legs and body. The aedes aegypti mosquito is also called the yellow fever mosquito. Unlike most mosquitoes it bites in daytime and indoors as well as outdoors. This mosquito also can carry dengue.
B. A device to level uneven surfaces
(they used concrete to level the ground)
