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