Questions & Answers about Вокруг дома растут деревья.
Because вокруг (around) always requires the genitive case.
- дом = nominative (dictionary form)
- дома = genitive singular of дом
Many Russian prepositions require a specific case. Вокруг is one of those that always takes the genitive:
- вокруг дома – around the house
- вокруг школы – around the school
- вокруг города – around the city
So you must say вокруг дома, never вокруг дом.