could sterilise
Regular verb: sterilise - sterilised- sterilised

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could sterilise
you could sterilise
he could sterilise
we could sterilise
you could sterilise
they could sterilise 	I could be sterilising
you could be sterilising
he could be sterilising
we could be sterilising
you could be sterilising
they could be sterilising	I could have sterilised
you could have sterilised
he could have sterilised
we could have sterilised
you could have sterilised
they could have sterilised	I could have been sterilising
you could have been sterilising
he could have been sterilising
we could have been sterilising
you could have been sterilising
they could have been sterilising	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't sterilise
you couldn't sterilise
he couldn't sterilise
we couldn't sterilise
you couldn't sterilise
they couldn't sterilise 	I couldn't be sterilising
you couldn't be sterilising
he couldn't be sterilising
we couldn't be sterilising
you couldn't be sterilising
they couldn't be sterilising	I couldn't have sterilised
you couldn't have sterilised
he couldn't have sterilised
we couldn't have sterilised
you couldn't have sterilised
they couldn't have sterilised	I couldn't have been sterilising
you couldn't have been sterilising
he couldn't have been sterilising
we couldn't have been sterilising
you couldn't have been sterilising
they couldn't have been sterilising	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I sterilise?
could you sterilise?
could he sterilise?
could we sterilise?
could you sterilise?
could they sterilise? 	could I be sterilising?
could you be sterilising?
could he be sterilising?
could we be sterilising?
could you be sterilising?
could they be sterilising? 	could I have sterilised?
could you have sterilised?
could he have sterilised?
could we have sterilised?
could you have sterilised?
could they have sterilised? 	could I have been sterilising?
could you have been sterilising?
could he have been sterilising?
could we have been sterilising?
could you have been sterilising?
could they have been sterilising? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I sterilise?
couldn't you sterilise?
couldn't he sterilise?
couldn't we sterilise?
couldn't you sterilise?
couldn't they sterilise? 	couldn't I be sterilising?
couldn't you be sterilising?
couldn't he be sterilising?
couldn't we be sterilising?
couldn't you be sterilising?
couldn't they be sterilising? 	couldn't I have sterilised?
couldn't you have sterilised?
couldn't he have sterilised?
couldn't we have sterilised?
couldn't you have sterilised?
couldn't they have sterilised? 	couldn't I have been sterilising?
couldn't you have been sterilising?
couldn't he have been sterilising?
couldn't we have been sterilising?
couldn't you have been sterilising?
couldn't they have been sterilising?