could sterilise
Regular verb: sterilise - sterilised- sterilised

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could sterilise
you could sterilise
she could sterilise
we could sterilise
you could sterilise
they could sterilise 	I could be sterilising
you could be sterilising
she could be sterilising
we could be sterilising
you could be sterilising
they could be sterilising	I could have sterilised
you could have sterilised
she 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
she 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
she 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
she 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
she 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
she 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 she sterilise?
could we sterilise?
could you sterilise?
could they sterilise? 	could I be sterilising?
could you be sterilising?
could she be sterilising?
could we be sterilising?
could you be sterilising?
could they be sterilising? 	could I have sterilised?
could you have sterilised?
could she 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 she 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 she 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 she 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 she 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 she have been sterilising?
couldn't we have been sterilising?
couldn't you have been sterilising?
couldn't they have been sterilising?