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