I could refract you could refract he could refract we could refract you could refract they could refract
V-ing form
I could be refracting you could be refracting he could be refracting we could be refracting you could be refracting they could be refracting
Perfect
I could have refracted you could have refracted he could have refracted we could have refracted you could have refracted they could have refracted
V-ing perfect
I could have been refracting you could have been refracting he could have been refracting we could have been refracting you could have been refracting they could have been refracting
Negation
Simple form
I could not refract you could not refract he could not refract we could not refract you could not refract they could not refract
V-ing form
I could not be refracting you could not be refracting he could not be refracting we could not be refracting you could not be refracting they could not be refracting
Perfect
I could not have refracted you could not have refracted he could not have refracted we could not have refracted you could not have refracted they could not have refracted
V-ing perfect
I could not have been refracting you could not have been refracting he could not have been refracting we could not have been refracting you could not have been refracting they could not have been refracting
Interrogative form
Simple form
could I refract? could you refract? could he refract? could we refract? could you refract? could they refract?
V-ing form
could I be refracting? could you be refracting? could he be refracting? could we be refracting? could you be refracting? could they be refracting?
Perfect
could I have refracted? could you have refracted? could he have refracted? could we have refracted? could you have refracted? could they have refracted?
V-ing perfect
could I have been refracting? could you have been refracting? could he have been refracting? could we have been refracting? could you have been refracting? could they have been refracting?
Interro-negative form
Simple form
could I not refract? could you not refract? could he not refract? could we not refract? could you not refract? could they not refract?
V-ing form
could I not be refracting? could you not be refracting? could he not be refracting? could we not be refracting? could you not be refracting? could they not be refracting?
Perfect
could I not have refracted? could you not have refracted? could he not have refracted? could we not have refracted? could you not have refracted? could they not have refracted?
V-ing perfect
could I not have been refracting? could you not have been refracting? could he not have been refracting? could we not have been refracting? could you not have been refracting? could they not have been refracting?