I could snowball you could snowball he could snowball we could snowball you could snowball they could snowball
V-ing form
I could be snowballing you could be snowballing he could be snowballing we could be snowballing you could be snowballing they could be snowballing
Perfect
I could have snowballed you could have snowballed he could have snowballed we could have snowballed you could have snowballed they could have snowballed
V-ing perfect
I could have been snowballing you could have been snowballing he could have been snowballing we could have been snowballing you could have been snowballing they could have been snowballing
Negation
Simple form
I could not snowball you could not snowball he could not snowball we could not snowball you could not snowball they could not snowball
V-ing form
I could not be snowballing you could not be snowballing he could not be snowballing we could not be snowballing you could not be snowballing they could not be snowballing
Perfect
I could not have snowballed you could not have snowballed he could not have snowballed we could not have snowballed you could not have snowballed they could not have snowballed
V-ing perfect
I could not have been snowballing you could not have been snowballing he could not have been snowballing we could not have been snowballing you could not have been snowballing they could not have been snowballing
Interrogative form
Simple form
could I snowball? could you snowball? could he snowball? could we snowball? could you snowball? could they snowball?
V-ing form
could I be snowballing? could you be snowballing? could he be snowballing? could we be snowballing? could you be snowballing? could they be snowballing?
Perfect
could I have snowballed? could you have snowballed? could he have snowballed? could we have snowballed? could you have snowballed? could they have snowballed?
V-ing perfect
could I have been snowballing? could you have been snowballing? could he have been snowballing? could we have been snowballing? could you have been snowballing? could they have been snowballing?
Interro-negative form
Simple form
could I not snowball? could you not snowball? could he not snowball? could we not snowball? could you not snowball? could they not snowball?
V-ing form
could I not be snowballing? could you not be snowballing? could he not be snowballing? could we not be snowballing? could you not be snowballing? could they not be snowballing?
Perfect
could I not have snowballed? could you not have snowballed? could he not have snowballed? could we not have snowballed? could you not have snowballed? could they not have snowballed?
V-ing perfect
could I not have been snowballing? could you not have been snowballing? could he not have been snowballing? could we not have been snowballing? could you not have been snowballing? could they not have been snowballing?