English verb conjugation
CAN FAIL

Regular verb: fail - failed - failed

Affirmation

Simple form	V-ing form
I can fail you can fail he can fail we can fail you can fail they can fail	I can be failing you can be failing he can be failing we can be failing you can be failing they can be failing
Perfect	V-ing perfect
I can have failed you can have failed he can have failed we can have failed you can have failed they can have failed	I can have been failing you can have been failing he can have been failing we can have been failing you can have been failing they can have been failing

Negation

Simple form	V-ing form
I cannot fail you cannot fail he cannot fail we cannot fail you cannot fail they cannot fail	I cannot be failing you cannot be failing he cannot be failing we cannot be failing you cannot be failing they cannot be failing
Perfect	V-ing perfect
I cannot have failed you cannot have failed he cannot have failed we cannot have failed you cannot have failed they cannot have failed	I cannot have been failing you cannot have been failing he cannot have been failing we cannot have been failing you cannot have been failing they cannot have been failing

Interrogative form

Simple form	V-ing form
can I fail? can you fail? can he fail? can we fail? can you fail? can they fail?	can I be failing? can you be failing? can he be failing? can we be failing? can you be failing? can they be failing?
Perfect	V-ing perfect
can I have failed? can you have failed? can he have failed? can we have failed? can you have failed? can they have failed?	can I have been failing? can you have been failing? can he have been failing? can we have been failing? can you have been failing? can they have been failing?

Interro-negative form

Simple form	V-ing form
can I not fail? can you not fail? can he not fail? can we not fail? can you not fail? can they not fail?	can I not be failing? can you not be failing? can he not be failing? can we not be failing? can you not be failing? can they not be failing?
Perfect	V-ing perfect
can I not have failed? can you not have failed? can he not have failed? can we not have failed? can you not have failed? can they not have failed?	can I not have been failing? can you not have been failing? can he not have been failing? can we not have been failing? can you not have been failing? can they not have been failing?