КАКОЙ ПАДЕЖ У СЛОВА      ОБОГРЕВА    А ПРЕДЛОЖЕНИЕ ТАКОЕ : Первобытные люди долго высекали  огонь для обогрева.

He asked me to stop the car.She told him to come at 5.She asked me to open the window.I asked her to bring me a glass of water.The commander asked him to take the prisoner away.He asked me not to go there.Mum told me to clear my room.They asked us not to run in the corridor.The teacher asked the students to do all the homework in time.The instructor says not to turn on this road.

огонь для (кого? чего?) обогрева - р.п.

Родительный падеш сто працентов