This week I have started with my further education to foreign language correspondent English by distance learning. Directly after beginning to learn and do some exercises I'm dispear of the usage of "have to" and "must".
Joanne is writing a letter to her best friend. In this letter she will infom her friend about the rules of the international house where she spend her holidays. The rules are given, and I should finish the letter with modal auxilaries.
I always used "have to" for things, which she have to do. But the books answer is always "must"
She have to clean the bath after use.
She must clean the bath after use.
I'm really confused Could you please explain to me, why "have to" is incorrect?