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