1. I must go to the doctor because I have a terrible stomach-ache.
2. Peter!, you must be quiet to stay in the library.
3. Maria must go to school every day because she is ten years old and it's compulsory.
4. Yesterday I had to work hard and I was very tired in the evening.
5. Ainoa has to wear glasses for reading and watching television.
6. She has to get up early because she starts work at six o'clock.