1.They don't allow tourists to cross the desert alone Tourists must't 2. It's necessary for travellers to make a reservation Travellers must sao thế

1.They don't allow tourists to cross the desert alone
Tourists must't cross the desert alone.

2. It's necessary for travellers to make a reservation.

Travellers must make a reservation.

- allow sb + to V : cho phép ai đó làm gì

- mustn't +V-inf: ko đc lmj ( mang  tính cấm đoán)

- must +V-inf: phải lmj ( mang tính bắt buộc)