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 can't mask you can't mask he can't mask we can't mask you can't mask they can't mask	I can't be masking you can't be masking he can't be masking we can't be masking you can't be masking they can't be masking
Perfect	V-ing perfect
I can't have masked you can't have masked he can't have masked we can't have masked you can't have masked they can't have masked	I can't have been masking you can't have been masking he can't have been masking we can't have been masking you can't have been masking they can't 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't I mask? can't you mask? can't he mask? can't we mask? can't you mask? can't they mask?	can't I be masking? can't you be masking? can't he be masking? can't we be masking? can't you be masking? can't they be masking?
Perfect	V-ing perfect
can't I have masked? can't you have masked? can't he have masked? can't we have masked? can't you have masked? can't they have masked?	can't I have been masking? can't you have been masking? can't he have been masking? can't we have been masking? can't you have been masking? can't they have been masking?