How to Say "Why do you have to buy vegetables?" in Korean?

"Why do you have to buy vegetables?" in Korean is 왜 채소 사야 돼요? (wae chaeso saya dwaeyo)

마트 (mateu) - Supermarket
일요일 (iryoil) - Sunday
일요일에 마트 가요. (iryoire mateu gayo) - I go to the supermarket on Sunday.
냉장고에 음식 없어요. (naengjanggoe eumsik eopsseoyo) - There's no food in the fridge.
그래서 마트 가야 돼요. (geuraeseo mateu gaya dwaeyo) - So I have to go to the supermarket.
음식 사야 돼요. (eumsik saya dwaeyo) - I have to buy food.
내일 마트에서 뭐 사야 돼요? (naeil mateueseo mwo saya dwaeyo) - What do we have to buy at the supermarket tomorrow?
과일 사야 돼요. (gwail saya dwaeyo) - I have to buy fruit.