I could smoke you could smoke he could smoke we could smoke you could smoke they could smoke
V-ing form
I could be smoking you could be smoking he could be smoking we could be smoking you could be smoking they could be smoking
Perfect
I could have smoked you could have smoked he 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 he 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 he 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 he 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 he 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 he 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 he smoke? could we smoke? could you smoke? could they smoke?
V-ing form
could I be smoking? could you be smoking? could he be smoking? could we be smoking? could you be smoking? could they be smoking?
Perfect
could I have smoked? could you have smoked? could he 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 he 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 he 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 he 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 he 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 he have been smoking? couldn't we have been smoking? couldn't you have been smoking? couldn't they have been smoking?