Use "must," "mustn't," "needn't," "have," "should," "shouldn't":

-- Well, kids, this is Kelly, your baby-sitter for the time we're away. You 1)... be nice to her. Dad and I are sorry we 2)... leave you for a month, but we really 3)....
-- Hi, you 4)... be Sam, and this 5)... be the little Nancy.
-- Oh, you 6)... be so noisy. Come, Kelly, we 7)... show you around the house. You 8)... do a lot of work. The only thing you 9)... do is feed them on time and look after them during the day.
-- 10)... I go shopping?
-- No, you 11)..., we have a housekeeper and a maid.
-- 12)...I wash up?
-- No, you 13)..., you 14)... do any work about the house.
-- What time 15)... I come in the morning?
-- You 16)... come at 9 and stay till 5, but you 17)... be late in the morning, and you 18)... allow Sam to stay out in the garden long You 19)... be firm about it. If anything goes wrong, you 20)... phone us
-- You 21)... worry, I'll do my best.