I can sift you can sift he can sift we can sift you can sift they can sift
V-ing form
I can be sifting you can be sifting he can be sifting we can be sifting you can be sifting they can be sifting
Perfect
I can have sifted you can have sifted he can have sifted we can have sifted you can have sifted they can have sifted
V-ing perfect
I can have been sifting you can have been sifting he can have been sifting we can have been sifting you can have been sifting they can have been sifting
Negation
Simple form
I cannot sift you cannot sift he cannot sift we cannot sift you cannot sift they cannot sift
V-ing form
I cannot be sifting you cannot be sifting he cannot be sifting we cannot be sifting you cannot be sifting they cannot be sifting
Perfect
I cannot have sifted you cannot have sifted he cannot have sifted we cannot have sifted you cannot have sifted they cannot have sifted
V-ing perfect
I cannot have been sifting you cannot have been sifting he cannot have been sifting we cannot have been sifting you cannot have been sifting they cannot have been sifting
Interrogative form
Simple form
can I sift? can you sift? can he sift? can we sift? can you sift? can they sift?
V-ing form
can I be sifting? can you be sifting? can he be sifting? can we be sifting? can you be sifting? can they be sifting?
Perfect
can I have sifted? can you have sifted? can he have sifted? can we have sifted? can you have sifted? can they have sifted?
V-ing perfect
can I have been sifting? can you have been sifting? can he have been sifting? can we have been sifting? can you have been sifting? can they have been sifting?
Interro-negative form
Simple form
can I not sift? can you not sift? can he not sift? can we not sift? can you not sift? can they not sift?
V-ing form
can I not be sifting? can you not be sifting? can he not be sifting? can we not be sifting? can you not be sifting? can they not be sifting?
Perfect
can I not have sifted? can you not have sifted? can he not have sifted? can we not have sifted? can you not have sifted? can they not have sifted?
V-ing perfect
can I not have been sifting? can you not have been sifting? can he not have been sifting? can we not have been sifting? can you not have been sifting? can they not have been sifting?