I can improve you can improve he can improve we can improve you can improve they can improve
V-ing form
I can be improving you can be improving he can be improving we can be improving you can be improving they can be improving
Perfect
I can have improved you can have improved he can have improved we can have improved you can have improved they can have improved
V-ing perfect
I can have been improving you can have been improving he can have been improving we can have been improving you can have been improving they can have been improving
Negation
Simple form
I can't improve you can't improve he can't improve we can't improve you can't improve they can't improve
V-ing form
I can't be improving you can't be improving he can't be improving we can't be improving you can't be improving they can't be improving
Perfect
I can't have improved you can't have improved he can't have improved we can't have improved you can't have improved they can't have improved
V-ing perfect
I can't have been improving you can't have been improving he can't have been improving we can't have been improving you can't have been improving they can't have been improving
Interrogative form
Simple form
can I improve? can you improve? can he improve? can we improve? can you improve? can they improve?
V-ing form
can I be improving? can you be improving? can he be improving? can we be improving? can you be improving? can they be improving?
Perfect
can I have improved? can you have improved? can he have improved? can we have improved? can you have improved? can they have improved?
V-ing perfect
can I have been improving? can you have been improving? can he have been improving? can we have been improving? can you have been improving? can they have been improving?
Interro-negative form
Simple form
can't I improve? can't you improve? can't he improve? can't we improve? can't you improve? can't they improve?
V-ing form
can't I be improving? can't you be improving? can't he be improving? can't we be improving? can't you be improving? can't they be improving?
Perfect
can't I have improved? can't you have improved? can't he have improved? can't we have improved? can't you have improved? can't they have improved?
V-ing perfect
can't I have been improving? can't you have been improving? can't he have been improving? can't we have been improving? can't you have been improving? can't they have been improving?