could sterilize
Regular verb: sterilize - sterilized- sterilized

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could sterilize
you could sterilize
he could sterilize
we could sterilize
you could sterilize
they could sterilize 	I could be sterilizing
you could be sterilizing
he could be sterilizing
we could be sterilizing
you could be sterilizing
they could be sterilizing	I could have sterilized
you could have sterilized
he could have sterilized
we could have sterilized
you could have sterilized
they could have sterilized	I could have been sterilizing
you could have been sterilizing
he could have been sterilizing
we could have been sterilizing
you could have been sterilizing
they could have been sterilizing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't sterilize
you couldn't sterilize
he couldn't sterilize
we couldn't sterilize
you couldn't sterilize
they couldn't sterilize 	I couldn't be sterilizing
you couldn't be sterilizing
he couldn't be sterilizing
we couldn't be sterilizing
you couldn't be sterilizing
they couldn't be sterilizing	I couldn't have sterilized
you couldn't have sterilized
he couldn't have sterilized
we couldn't have sterilized
you couldn't have sterilized
they couldn't have sterilized	I couldn't have been sterilizing
you couldn't have been sterilizing
he couldn't have been sterilizing
we couldn't have been sterilizing
you couldn't have been sterilizing
they couldn't have been sterilizing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I sterilize?
could you sterilize?
could he sterilize?
could we sterilize?
could you sterilize?
could they sterilize? 	could I be sterilizing?
could you be sterilizing?
could he be sterilizing?
could we be sterilizing?
could you be sterilizing?
could they be sterilizing? 	could I have sterilized?
could you have sterilized?
could he have sterilized?
could we have sterilized?
could you have sterilized?
could they have sterilized? 	could I have been sterilizing?
could you have been sterilizing?
could he have been sterilizing?
could we have been sterilizing?
could you have been sterilizing?
could they have been sterilizing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I sterilize?
couldn't you sterilize?
couldn't he sterilize?
couldn't we sterilize?
couldn't you sterilize?
couldn't they sterilize? 	couldn't I be sterilizing?
couldn't you be sterilizing?
couldn't he be sterilizing?
couldn't we be sterilizing?
couldn't you be sterilizing?
couldn't they be sterilizing? 	couldn't I have sterilized?
couldn't you have sterilized?
couldn't he have sterilized?
couldn't we have sterilized?
couldn't you have sterilized?
couldn't they have sterilized? 	couldn't I have been sterilizing?
couldn't you have been sterilizing?
couldn't he have been sterilizing?
couldn't we have been sterilizing?
couldn't you have been sterilizing?
couldn't they have been sterilizing?