can occur
Regular verb: occur - occurred- occurred

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can occur
you can occur
she can occur
we can occur
you can occur
they can occur 	I can be occurring
you can be occurring
she can be occurring
we can be occurring
you can be occurring
they can be occurring	I can have occurred
you can have occurred
she can have occurred
we can have occurred
you can have occurred
they can have occurred	I can have been occurring
you can have been occurring
she can have been occurring
we can have been occurring
you can have been occurring
they can have been occurring	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can't occur
you can't occur
she can't occur
we can't occur
you can't occur
they can't occur 	I can't be occurring
you can't be occurring
she can't be occurring
we can't be occurring
you can't be occurring
they can't be occurring	I can't have occurred
you can't have occurred
she can't have occurred
we can't have occurred
you can't have occurred
they can't have occurred	I can't have been occurring
you can't have been occurring
she can't have been occurring
we can't have been occurring
you can't have been occurring
they can't have been occurring	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I occur?
can you occur?
can she occur?
can we occur?
can you occur?
can they occur? 	can I be occurring?
can you be occurring?
can she be occurring?
can we be occurring?
can you be occurring?
can they be occurring? 	can I have occurred?
can you have occurred?
can she have occurred?
can we have occurred?
can you have occurred?
can they have occurred? 	can I have been occurring?
can you have been occurring?
can she have been occurring?
can we have been occurring?
can you have been occurring?
can they have been occurring? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can't I occur?
can't you occur?
can't she occur?
can't we occur?
can't you occur?
can't they occur? 	can't I be occurring?
can't you be occurring?
can't she be occurring?
can't we be occurring?
can't you be occurring?
can't they be occurring? 	can't I have occurred?
can't you have occurred?
can't she have occurred?
can't we have occurred?
can't you have occurred?
can't they have occurred? 	can't I have been occurring?
can't you have been occurring?
can't she have been occurring?
can't we have been occurring?
can't you have been occurring?
can't they have been occurring?