I could muss you could muss he could muss we could muss you could muss they could muss
V-ing form
I could be mussing you could be mussing he could be mussing we could be mussing you could be mussing they could be mussing
Perfect
I could have mussed you could have mussed he could have mussed we could have mussed you could have mussed they could have mussed
V-ing perfect
I could have been mussing you could have been mussing he could have been mussing we could have been mussing you could have been mussing they could have been mussing
Negation
Simple form
I couldn't muss you couldn't muss he couldn't muss we couldn't muss you couldn't muss they couldn't muss
V-ing form
I couldn't be mussing you couldn't be mussing he couldn't be mussing we couldn't be mussing you couldn't be mussing they couldn't be mussing
Perfect
I couldn't have mussed you couldn't have mussed he couldn't have mussed we couldn't have mussed you couldn't have mussed they couldn't have mussed
V-ing perfect
I couldn't have been mussing you couldn't have been mussing he couldn't have been mussing we couldn't have been mussing you couldn't have been mussing they couldn't have been mussing
Interrogative form
Simple form
could I muss? could you muss? could he muss? could we muss? could you muss? could they muss?
V-ing form
could I be mussing? could you be mussing? could he be mussing? could we be mussing? could you be mussing? could they be mussing?
Perfect
could I have mussed? could you have mussed? could he have mussed? could we have mussed? could you have mussed? could they have mussed?
V-ing perfect
could I have been mussing? could you have been mussing? could he have been mussing? could we have been mussing? could you have been mussing? could they have been mussing?
Interro-negative form
Simple form
couldn't I muss? couldn't you muss? couldn't he muss? couldn't we muss? couldn't you muss? couldn't they muss?
V-ing form
couldn't I be mussing? couldn't you be mussing? couldn't he be mussing? couldn't we be mussing? couldn't you be mussing? couldn't they be mussing?
Perfect
couldn't I have mussed? couldn't you have mussed? couldn't he have mussed? couldn't we have mussed? couldn't you have mussed? couldn't they have mussed?
V-ing perfect
couldn't I have been mussing? couldn't you have been mussing? couldn't he have been mussing? couldn't we have been mussing? couldn't you have been mussing? couldn't they have been mussing?