We brought books,so I hope they will bring
(3.)theirs
its number three because if you stated i hope they will bring their ..... its incomplete
or if you put i hope i bring them ..... its just not sounding right...
Quad is a root word for four so quadruplex would mean four screens.
"Today nobody brought his or her instrument" is correct. It is common for people to use "their" in a sentence like this, but "his or her" is the more proper term.
They feel comfortable in their own current positions and only care about privilege if it actually affects/bothers themselves.