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