must occur
Verbo regular: occur - occurred- occurred

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must occur
you must occur
he must occur
we must occur
you must occur
they must occur 	I must be occurring
you must be occurring
he must be occurring
we must be occurring
you must be occurring
they must be occurring	I must have occurred
you must have occurred
he must have occurred
we must have occurred
you must have occurred
they must have occurred	I must have been occurring
you must have been occurring
he must have been occurring
we must have been occurring
you must have been occurring
they must have been occurring	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must not occur
you must not occur
he must not occur
we must not occur
you must not occur
they must not occur 	I must not be occurring
you must not be occurring
he must not be occurring
we must not be occurring
you must not be occurring
they must not be occurring	I must not have occurred
you must not have occurred
he must not have occurred
we must not have occurred
you must not have occurred
they must not have occurred	I must not have been occurring
you must not have been occurring
he must not have been occurring
we must not have been occurring
you must not have been occurring
they must not have been occurring	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I occur?
must you occur?
must he occur?
must we occur?
must you occur?
must they occur? 	must I be occurring?
must you be occurring?
must he be occurring?
must we be occurring?
must you be occurring?
must they be occurring? 	must I have occurred?
must you have occurred?
must he have occurred?
must we have occurred?
must you have occurred?
must they have occurred? 	must I have been occurring?
must you have been occurring?
must he have been occurring?
must we have been occurring?
must you have been occurring?
must they have been occurring? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I not occur?
must you not occur?
must he not occur?
must we not occur?
must you not occur?
must they not occur? 	must I not be occurring?
must you not be occurring?
must he not be occurring?
must we not be occurring?
must you not be occurring?
must they not be occurring? 	must I not have occurred?
must you not have occurred?
must he not have occurred?
must we not have occurred?
must you not have occurred?
must they not have occurred? 	must I not have been occurring?
must you not have been occurring?
must he not have been occurring?
must we not have been occurring?
must you not have been occurring?
must they not have been occurring?