I can burr you can burr he can burr we can burr you can burr they can burr
V-ing form
I can be burring you can be burring he can be burring we can be burring you can be burring they can be burring
Perfect
I can have burred you can have burred he can have burred we can have burred you can have burred they can have burred
V-ing perfect
I can have been burring you can have been burring he can have been burring we can have been burring you can have been burring they can have been burring
Negation
Simple form
I cannot burr you cannot burr he cannot burr we cannot burr you cannot burr they cannot burr
V-ing form
I cannot be burring you cannot be burring he cannot be burring we cannot be burring you cannot be burring they cannot be burring
Perfect
I cannot have burred you cannot have burred he cannot have burred we cannot have burred you cannot have burred they cannot have burred
V-ing perfect
I cannot have been burring you cannot have been burring he cannot have been burring we cannot have been burring you cannot have been burring they cannot have been burring
Interrogative form
Simple form
can I burr? can you burr? can he burr? can we burr? can you burr? can they burr?
V-ing form
can I be burring? can you be burring? can he be burring? can we be burring? can you be burring? can they be burring?
Perfect
can I have burred? can you have burred? can he have burred? can we have burred? can you have burred? can they have burred?
V-ing perfect
can I have been burring? can you have been burring? can he have been burring? can we have been burring? can you have been burring? can they have been burring?
Interro-negative form
Simple form
can I not burr? can you not burr? can he not burr? can we not burr? can you not burr? can they not burr?
V-ing form
can I not be burring? can you not be burring? can he not be burring? can we not be burring? can you not be burring? can they not be burring?
Perfect
can I not have burred? can you not have burred? can he not have burred? can we not have burred? can you not have burred? can they not have burred?
V-ing perfect
can I not have been burring? can you not have been burring? can he not have been burring? can we not have been burring? can you not have been burring? can they not have been burring?