English verb conjugation
COULD START

Regular verb: start - started - started

Affirmation

Simple form	V-ing form
I could start you could start he could start we could start you could start they could start	I could be starting you could be starting he could be starting we could be starting you could be starting they could be starting
Perfect	V-ing perfect
I could have started you could have started he could have started we could have started you could have started they could have started	I could have been starting you could have been starting he could have been starting we could have been starting you could have been starting they could have been starting

Negation

Simple form	V-ing form
I couldn't start you couldn't start he couldn't start we couldn't start you couldn't start they couldn't start	I couldn't be starting you couldn't be starting he couldn't be starting we couldn't be starting you couldn't be starting they couldn't be starting
Perfect	V-ing perfect
I couldn't have started you couldn't have started he couldn't have started we couldn't have started you couldn't have started they couldn't have started	I couldn't have been starting you couldn't have been starting he couldn't have been starting we couldn't have been starting you couldn't have been starting they couldn't have been starting

Interrogative form

Simple form	V-ing form
could I start? could you start? could he start? could we start? could you start? could they start?	could I be starting? could you be starting? could he be starting? could we be starting? could you be starting? could they be starting?
Perfect	V-ing perfect
could I have started? could you have started? could he have started? could we have started? could you have started? could they have started?	could I have been starting? could you have been starting? could he have been starting? could we have been starting? could you have been starting? could they have been starting?

Interro-negative form

Simple form	V-ing form
couldn't I start? couldn't you start? couldn't he start? couldn't we start? couldn't you start? couldn't they start?	couldn't I be starting? couldn't you be starting? couldn't he be starting? couldn't we be starting? couldn't you be starting? couldn't they be starting?
Perfect	V-ing perfect
couldn't I have started? couldn't you have started? couldn't he have started? couldn't we have started? couldn't you have started? couldn't they have started?	couldn't I have been starting? couldn't you have been starting? couldn't he have been starting? couldn't we have been starting? couldn't you have been starting? couldn't they have been starting?