I can dull you can dull he can dull we can dull you can dull they can dull
V-ing form
I can be dulling you can be dulling he can be dulling we can be dulling you can be dulling they can be dulling
Perfect
I can have dulled you can have dulled he can have dulled we can have dulled you can have dulled they can have dulled
V-ing perfect
I can have been dulling you can have been dulling he can have been dulling we can have been dulling you can have been dulling they can have been dulling
Negation
Simple form
I can't dull you can't dull he can't dull we can't dull you can't dull they can't dull
V-ing form
I can't be dulling you can't be dulling he can't be dulling we can't be dulling you can't be dulling they can't be dulling
Perfect
I can't have dulled you can't have dulled he can't have dulled we can't have dulled you can't have dulled they can't have dulled
V-ing perfect
I can't have been dulling you can't have been dulling he can't have been dulling we can't have been dulling you can't have been dulling they can't have been dulling
Interrogative form
Simple form
can I dull? can you dull? can he dull? can we dull? can you dull? can they dull?
V-ing form
can I be dulling? can you be dulling? can he be dulling? can we be dulling? can you be dulling? can they be dulling?
Perfect
can I have dulled? can you have dulled? can he have dulled? can we have dulled? can you have dulled? can they have dulled?
V-ing perfect
can I have been dulling? can you have been dulling? can he have been dulling? can we have been dulling? can you have been dulling? can they have been dulling?
Interro-negative form
Simple form
can't I dull? can't you dull? can't he dull? can't we dull? can't you dull? can't they dull?
V-ing form
can't I be dulling? can't you be dulling? can't he be dulling? can't we be dulling? can't you be dulling? can't they be dulling?
Perfect
can't I have dulled? can't you have dulled? can't he have dulled? can't we have dulled? can't you have dulled? can't they have dulled?
V-ing perfect
can't I have been dulling? can't you have been dulling? can't he have been dulling? can't we have been dulling? can't you have been dulling? can't they have been dulling?