Составьте 4 вопроса времени (альт., общ., раздел., к подл) they must help their grandparents.

They must help their grandparents.

did they have to help their grandparents? общ
did they have to help their grandparents or parents? альт
They had to help their grandparents, mustn't they? разд
who had to help their grandparents? к подл