must happen
Verbo regular: happen - happened- happened

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
-
-
it must happen
-
-
- 	-
-
it must be happening
-
-
- 	-
-
it must have happened
-
-
- 	-
-
it must have been happening
-
-
- 	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
-
-
it mustn't happen
-
-
- 	-
-
it mustn't be happening
-
-
- 	-
-
it mustn't have happened
-
-
- 	-
-
it mustn't have been happening
-
-
- 	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
-
-
must it happen?
-
-
- 	-
-
must it be happening?
-
-
- 	-
-
must it have happened?
-
-
- 	-
-
must it have been happening?
-
-
- 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
-
-
mustn't it happen?
-
-
- 	-
-
mustn't it be happening?
-
-
- 	-
-
mustn't it have happened?
-
-
- 	-
-
mustn't it have been happening?
-
-
-