Questions & Answers about Matična ploča i čvrsti disk su u laptopu.
Because the subject is plural.
The sentence has two things:
- matična ploča = motherboard
- čvrsti disk = hard drive
They are linked by i = and, so together they form a plural subject: the motherboard and the hard drive.
That is why Serbian uses su = are, not je = is.
- ploča je = the board is
- disk je = the disk is
- ploča i disk su = the board and the disk are
Laptopu is in the locative singular.
After the preposition u when it means in or inside, Serbian usually takes the locative:
- u laptopu = in the laptop
- u kući = in the house
- u gradu = in the city
The base form is laptop. In the locative singular, many masculine nouns take -u:
- laptop → u laptopu
- grad → u gradu
So u laptopu literally means in the laptop.