Completar frases MUST and MUSTN'TVersión en línea Verbo modal de obligación y prohibición por Olga Marcela De la Torre Herrera 1 must must mustnt mustnt must 1 . You cross the road without looking . It's dangerous . 2 . The exam is next week . I revise . 3 . You forget your umbrella . It's going to rain . 4 . You learn to swim before you go sailing . 5 . I phone John tonight . I have not spoken to him for a long time .