I could harden you could harden she could harden we could harden you could harden they could harden
V-ing form
I could be hardening you could be hardening she could be hardening we could be hardening you could be hardening they could be hardening
Perfect
I could have hardened you could have hardened she could have hardened we could have hardened you could have hardened they could have hardened
V-ing perfect
I could have been hardening you could have been hardening she could have been hardening we could have been hardening you could have been hardening they could have been hardening
Negation
Simple form
I couldn't harden you couldn't harden she couldn't harden we couldn't harden you couldn't harden they couldn't harden
V-ing form
I couldn't be hardening you couldn't be hardening she couldn't be hardening we couldn't be hardening you couldn't be hardening they couldn't be hardening
Perfect
I couldn't have hardened you couldn't have hardened she couldn't have hardened we couldn't have hardened you couldn't have hardened they couldn't have hardened
V-ing perfect
I couldn't have been hardening you couldn't have been hardening she couldn't have been hardening we couldn't have been hardening you couldn't have been hardening they couldn't have been hardening
Interrogative form
Simple form
could I harden? could you harden? could she harden? could we harden? could you harden? could they harden?
V-ing form
could I be hardening? could you be hardening? could she be hardening? could we be hardening? could you be hardening? could they be hardening?
Perfect
could I have hardened? could you have hardened? could she have hardened? could we have hardened? could you have hardened? could they have hardened?
V-ing perfect
could I have been hardening? could you have been hardening? could she have been hardening? could we have been hardening? could you have been hardening? could they have been hardening?
Interro-negative form
Simple form
couldn't I harden? couldn't you harden? couldn't she harden? couldn't we harden? couldn't you harden? couldn't they harden?
V-ing form
couldn't I be hardening? couldn't you be hardening? couldn't she be hardening? couldn't we be hardening? couldn't you be hardening? couldn't they be hardening?
Perfect
couldn't I have hardened? couldn't you have hardened? couldn't she have hardened? couldn't we have hardened? couldn't you have hardened? couldn't they have hardened?
V-ing perfect
couldn't I have been hardening? couldn't you have been hardening? couldn't she have been hardening? couldn't we have been hardening? couldn't you have been hardening? couldn't they have been hardening?