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