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