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