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