I can fail you can fail she can fail we can fail you can fail they can fail
V-ing form
I can be failing you can be failing she can be failing we can be failing you can be failing they can be failing
Perfect
I can have failed you can have failed she can have failed we can have failed you can have failed they can have failed
V-ing perfect
I can have been failing you can have been failing she can have been failing we can have been failing you can have been failing they can have been failing
Negation
Simple form
I cannot fail you cannot fail she cannot fail we cannot fail you cannot fail they cannot fail
V-ing form
I cannot be failing you cannot be failing she cannot be failing we cannot be failing you cannot be failing they cannot be failing
Perfect
I cannot have failed you cannot have failed she cannot have failed we cannot have failed you cannot have failed they cannot have failed
V-ing perfect
I cannot have been failing you cannot have been failing she cannot have been failing we cannot have been failing you cannot have been failing they cannot have been failing
Interrogative form
Simple form
can I fail? can you fail? can she fail? can we fail? can you fail? can they fail?
V-ing form
can I be failing? can you be failing? can she be failing? can we be failing? can you be failing? can they be failing?
Perfect
can I have failed? can you have failed? can she have failed? can we have failed? can you have failed? can they have failed?
V-ing perfect
can I have been failing? can you have been failing? can she have been failing? can we have been failing? can you have been failing? can they have been failing?
Interro-negative form
Simple form
can I not fail? can you not fail? can she not fail? can we not fail? can you not fail? can they not fail?
V-ing form
can I not be failing? can you not be failing? can she not be failing? can we not be failing? can you not be failing? can they not be failing?
Perfect
can I not have failed? can you not have failed? can she not have failed? can we not have failed? can you not have failed? can they not have failed?
V-ing perfect
can I not have been failing? can you not have been failing? can she not have been failing? can we not have been failing? can you not have been failing? can they not have been failing?