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