I can drop you can drop he can drop we can drop you can drop they can drop
V-ing form
I can be dropping you can be dropping he can be dropping we can be dropping you can be dropping they can be dropping
Perfect
I can have dropped you can have dropped he can have dropped we can have dropped you can have dropped they can have dropped
V-ing perfect
I can have been dropping you can have been dropping he can have been dropping we can have been dropping you can have been dropping they can have been dropping
Negation
Simple form
I cannot drop you cannot drop he cannot drop we cannot drop you cannot drop they cannot drop
V-ing form
I cannot be dropping you cannot be dropping he cannot be dropping we cannot be dropping you cannot be dropping they cannot be dropping
Perfect
I cannot have dropped you cannot have dropped he cannot have dropped we cannot have dropped you cannot have dropped they cannot have dropped
V-ing perfect
I cannot have been dropping you cannot have been dropping he cannot have been dropping we cannot have been dropping you cannot have been dropping they cannot have been dropping
Interrogative form
Simple form
can I drop? can you drop? can he drop? can we drop? can you drop? can they drop?
V-ing form
can I be dropping? can you be dropping? can he be dropping? can we be dropping? can you be dropping? can they be dropping?
Perfect
can I have dropped? can you have dropped? can he have dropped? can we have dropped? can you have dropped? can they have dropped?
V-ing perfect
can I have been dropping? can you have been dropping? can he have been dropping? can we have been dropping? can you have been dropping? can they have been dropping?
Interro-negative form
Simple form
can I not drop? can you not drop? can he not drop? can we not drop? can you not drop? can they not drop?
V-ing form
can I not be dropping? can you not be dropping? can he not be dropping? can we not be dropping? can you not be dropping? can they not be dropping?
Perfect
can I not have dropped? can you not have dropped? can he not have dropped? can we not have dropped? can you not have dropped? can they not have dropped?
V-ing perfect
can I not have been dropping? can you not have been dropping? can he not have been dropping? can we not have been dropping? can you not have been dropping? can they not have been dropping?