English verb conjugation
COULD DULL

Regular verb: dull - dulled - dulled

Affirmation

Simple form	V-ing form
I could dull you could dull he could dull we could dull you could dull they could dull	I could be dulling you could be dulling he could be dulling we could be dulling you could be dulling they could be dulling
Perfect	V-ing perfect
I could have dulled you could have dulled he could have dulled we could have dulled you could have dulled they could have dulled	I could have been dulling you could have been dulling he could have been dulling we could have been dulling you could have been dulling they could have been dulling

Negation

Simple form	V-ing form
I could not dull you could not dull he could not dull we could not dull you could not dull they could not dull	I could not be dulling you could not be dulling he could not be dulling we could not be dulling you could not be dulling they could not be dulling
Perfect	V-ing perfect
I could not have dulled you could not have dulled he could not have dulled we could not have dulled you could not have dulled they could not have dulled	I could not have been dulling you could not have been dulling he could not have been dulling we could not have been dulling you could not have been dulling they could not have been dulling

Interrogative form

Simple form	V-ing form
could I dull? could you dull? could he dull? could we dull? could you dull? could they dull?	could I be dulling? could you be dulling? could he be dulling? could we be dulling? could you be dulling? could they be dulling?
Perfect	V-ing perfect
could I have dulled? could you have dulled? could he have dulled? could we have dulled? could you have dulled? could they have dulled?	could I have been dulling? could you have been dulling? could he have been dulling? could we have been dulling? could you have been dulling? could they have been dulling?

Interro-negative form

Simple form	V-ing form
could I not dull? could you not dull? could he not dull? could we not dull? could you not dull? could they not dull?	could I not be dulling? could you not be dulling? could he not be dulling? could we not be dulling? could you not be dulling? could they not be dulling?
Perfect	V-ing perfect
could I not have dulled? could you not have dulled? could he not have dulled? could we not have dulled? could you not have dulled? could they not have dulled?	could I not have been dulling? could you not have been dulling? could he not have been dulling? could we not have been dulling? could you not have been dulling? could they not have been dulling?