English verb conjugation
COULD MASK

Regular verb: mask - masked - masked

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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