English verb conjugation
COULD SIP

Regular verb: sip - sipped - sipped

Affirmation

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