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