I could flow you could flow he could flow we could flow you could flow they could flow
V-ing form
I could be flowing you could be flowing he could be flowing we could be flowing you could be flowing they could be flowing
Perfect
I could have flowed you could have flowed he could have flowed we could have flowed you could have flowed they could have flowed
V-ing perfect
I could have been flowing you could have been flowing he could have been flowing we could have been flowing you could have been flowing they could have been flowing
Negation
Simple form
I couldn't flow you couldn't flow he couldn't flow we couldn't flow you couldn't flow they couldn't flow
V-ing form
I couldn't be flowing you couldn't be flowing he couldn't be flowing we couldn't be flowing you couldn't be flowing they couldn't be flowing
Perfect
I couldn't have flowed you couldn't have flowed he couldn't have flowed we couldn't have flowed you couldn't have flowed they couldn't have flowed
V-ing perfect
I couldn't have been flowing you couldn't have been flowing he couldn't have been flowing we couldn't have been flowing you couldn't have been flowing they couldn't have been flowing
Interrogative form
Simple form
could I flow? could you flow? could he flow? could we flow? could you flow? could they flow?
V-ing form
could I be flowing? could you be flowing? could he be flowing? could we be flowing? could you be flowing? could they be flowing?
Perfect
could I have flowed? could you have flowed? could he have flowed? could we have flowed? could you have flowed? could they have flowed?
V-ing perfect
could I have been flowing? could you have been flowing? could he have been flowing? could we have been flowing? could you have been flowing? could they have been flowing?
Interro-negative form
Simple form
couldn't I flow? couldn't you flow? couldn't he flow? couldn't we flow? couldn't you flow? couldn't they flow?
V-ing form
couldn't I be flowing? couldn't you be flowing? couldn't he be flowing? couldn't we be flowing? couldn't you be flowing? couldn't they be flowing?
Perfect
couldn't I have flowed? couldn't you have flowed? couldn't he have flowed? couldn't we have flowed? couldn't you have flowed? couldn't they have flowed?
V-ing perfect
couldn't I have been flowing? couldn't you have been flowing? couldn't he have been flowing? couldn't we have been flowing? couldn't you have been flowing? couldn't they have been flowing?