I can sip you can sip she can sip we can sip you can sip they can sip
V-ing form
I can be sipping you can be sipping she can be sipping we can be sipping you can be sipping they can be sipping
Perfect
I can have sipped you can have sipped she can have sipped we can have sipped you can have sipped they can have sipped
V-ing perfect
I can have been sipping you can have been sipping she can have been sipping we can have been sipping you can have been sipping they can have been sipping
Negation
Simple form
I cannot sip you cannot sip she cannot sip we cannot sip you cannot sip they cannot sip
V-ing form
I cannot be sipping you cannot be sipping she cannot be sipping we cannot be sipping you cannot be sipping they cannot be sipping
Perfect
I cannot have sipped you cannot have sipped she cannot have sipped we cannot have sipped you cannot have sipped they cannot have sipped
V-ing perfect
I cannot have been sipping you cannot have been sipping she cannot have been sipping we cannot have been sipping you cannot have been sipping they cannot have been sipping
Interrogative form
Simple form
can I sip? can you sip? can she sip? can we sip? can you sip? can they sip?
V-ing form
can I be sipping? can you be sipping? can she be sipping? can we be sipping? can you be sipping? can they be sipping?
Perfect
can I have sipped? can you have sipped? can she have sipped? can we have sipped? can you have sipped? can they have sipped?
V-ing perfect
can I have been sipping? can you have been sipping? can she have been sipping? can we have been sipping? can you have been sipping? can they have been sipping?
Interro-negative form
Simple form
can I not sip? can you not sip? can she not sip? can we not sip? can you not sip? can they not sip?
V-ing form
can I not be sipping? can you not be sipping? can she not be sipping? can we not be sipping? can you not be sipping? can they not be sipping?
Perfect
can I not have sipped? can you not have sipped? can she not have sipped? can we not have sipped? can you not have sipped? can they not have sipped?
V-ing perfect
can I not have been sipping? can you not have been sipping? can she not have been sipping? can we not have been sipping? can you not have been sipping? can they not have been sipping?