I could button you could button she could button we could button you could button they could button
V-ing form
I could be buttoning you could be buttoning she could be buttoning we could be buttoning you could be buttoning they could be buttoning
Perfect
I could have buttoned you could have buttoned she could have buttoned we could have buttoned you could have buttoned they could have buttoned
V-ing perfect
I could have been buttoning you could have been buttoning she could have been buttoning we could have been buttoning you could have been buttoning they could have been buttoning
Negation
Simple form
I couldn't button you couldn't button she couldn't button we couldn't button you couldn't button they couldn't button
V-ing form
I couldn't be buttoning you couldn't be buttoning she couldn't be buttoning we couldn't be buttoning you couldn't be buttoning they couldn't be buttoning
Perfect
I couldn't have buttoned you couldn't have buttoned she couldn't have buttoned we couldn't have buttoned you couldn't have buttoned they couldn't have buttoned
V-ing perfect
I couldn't have been buttoning you couldn't have been buttoning she couldn't have been buttoning we couldn't have been buttoning you couldn't have been buttoning they couldn't have been buttoning
Interrogative form
Simple form
could I button? could you button? could she button? could we button? could you button? could they button?
V-ing form
could I be buttoning? could you be buttoning? could she be buttoning? could we be buttoning? could you be buttoning? could they be buttoning?
Perfect
could I have buttoned? could you have buttoned? could she have buttoned? could we have buttoned? could you have buttoned? could they have buttoned?
V-ing perfect
could I have been buttoning? could you have been buttoning? could she have been buttoning? could we have been buttoning? could you have been buttoning? could they have been buttoning?
Interro-negative form
Simple form
couldn't I button? couldn't you button? couldn't she button? couldn't we button? couldn't you button? couldn't they button?
V-ing form
couldn't I be buttoning? couldn't you be buttoning? couldn't she be buttoning? couldn't we be buttoning? couldn't you be buttoning? couldn't they be buttoning?
Perfect
couldn't I have buttoned? couldn't you have buttoned? couldn't she have buttoned? couldn't we have buttoned? couldn't you have buttoned? couldn't they have buttoned?
V-ing perfect
couldn't I have been buttoning? couldn't you have been buttoning? couldn't she have been buttoning? couldn't we have been buttoning? couldn't you have been buttoning? couldn't they have been buttoning?