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