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