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