English verb conjugation
CAN MASK

Regular verb: mask - masked - masked

Affirmation

Simple form	V-ing form
I can mask you can mask he can mask we can mask you can mask they can mask	I can be masking you can be masking he can be masking we can be masking you can be masking they can be masking
Perfect	V-ing perfect
I can have masked you can have masked he can have masked we can have masked you can have masked they can have masked	I can have been masking you can have been masking he can have been masking we can have been masking you can have been masking they can have been masking

Negation

Simple form	V-ing form
I cannot mask you cannot mask he cannot mask we cannot mask you cannot mask they cannot mask	I cannot be masking you cannot be masking he cannot be masking we cannot be masking you cannot be masking they cannot be masking
Perfect	V-ing perfect
I cannot have masked you cannot have masked he cannot have masked we cannot have masked you cannot have masked they cannot have masked	I cannot have been masking you cannot have been masking he cannot have been masking we cannot have been masking you cannot have been masking they cannot have been masking

Interrogative form

Simple form	V-ing form
can I mask? can you mask? can he mask? can we mask? can you mask? can they mask?	can I be masking? can you be masking? can he be masking? can we be masking? can you be masking? can they be masking?
Perfect	V-ing perfect
can I have masked? can you have masked? can he have masked? can we have masked? can you have masked? can they have masked?	can I have been masking? can you have been masking? can he have been masking? can we have been masking? can you have been masking? can they have been masking?

Interro-negative form

Simple form	V-ing form
can I not mask? can you not mask? can he not mask? can we not mask? can you not mask? can they not mask?	can I not be masking? can you not be masking? can he not be masking? can we not be masking? can you not be masking? can they not be masking?
Perfect	V-ing perfect
can I not have masked? can you not have masked? can he not have masked? can we not have masked? can you not have masked? can they not have masked?	can I not have been masking? can you not have been masking? can he not have been masking? can we not have been masking? can you not have been masking? can they not have been masking?