English verb conjugation
COULD MASK

Regular verb: mask - masked - masked

Affirmation

Simple form	V-ing form
I could mask you could mask she could mask we could mask you could mask they could mask	I could be masking you could be masking she 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 she 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 she 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 she 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 she 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 she 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 she 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 she mask? could we mask? could you mask? could they mask?	could I be masking? could you be masking? could she 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 she 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 she 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 she 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 she 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 she 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 she have been masking? couldn't we have been masking? couldn't you have been masking? couldn't they have been masking?