could sip
Regular verb: sip - sipped- sipped

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could sip
you could sip
she could sip
we could sip
you could sip
they could sip 	I could be sipping
you could be sipping
she could be sipping
we could be sipping
you could be sipping
they could be sipping	I could have sipped
you could have sipped
she could have sipped
we could have sipped
you could have sipped
they could have sipped	I could have been sipping
you could have been sipping
she could have been sipping
we could have been sipping
you could have been sipping
they could have been sipping	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't sip
you couldn't sip
she couldn't sip
we couldn't sip
you couldn't sip
they couldn't sip 	I couldn't be sipping
you couldn't be sipping
she couldn't be sipping
we couldn't be sipping
you couldn't be sipping
they couldn't be sipping	I couldn't have sipped
you couldn't have sipped
she couldn't have sipped
we couldn't have sipped
you couldn't have sipped
they couldn't have sipped	I couldn't have been sipping
you couldn't have been sipping
she couldn't have been sipping
we couldn't have been sipping
you couldn't have been sipping
they couldn't have been sipping	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I sip?
could you sip?
could she sip?
could we sip?
could you sip?
could they sip? 	could I be sipping?
could you be sipping?
could she be sipping?
could we be sipping?
could you be sipping?
could they be sipping? 	could I have sipped?
could you have sipped?
could she have sipped?
could we have sipped?
could you have sipped?
could they have sipped? 	could I have been sipping?
could you have been sipping?
could she have been sipping?
could we have been sipping?
could you have been sipping?
could they have been sipping? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I sip?
couldn't you sip?
couldn't she sip?
couldn't we sip?
couldn't you sip?
couldn't they sip? 	couldn't I be sipping?
couldn't you be sipping?
couldn't she be sipping?
couldn't we be sipping?
couldn't you be sipping?
couldn't they be sipping? 	couldn't I have sipped?
couldn't you have sipped?
couldn't she have sipped?
couldn't we have sipped?
couldn't you have sipped?
couldn't they have sipped? 	couldn't I have been sipping?
couldn't you have been sipping?
couldn't she have been sipping?
couldn't we have been sipping?
couldn't you have been sipping?
couldn't they have been sipping?