I can tree you can tree she can tree we can tree you can tree they can tree
V-ing form
I can be treeing you can be treeing she can be treeing we can be treeing you can be treeing they can be treeing
Perfect
I can have treed you can have treed she can have treed we can have treed you can have treed they can have treed
V-ing perfect
I can have been treeing you can have been treeing she can have been treeing we can have been treeing you can have been treeing they can have been treeing
Negation
Simple form
I cannot tree you cannot tree she cannot tree we cannot tree you cannot tree they cannot tree
V-ing form
I cannot be treeing you cannot be treeing she cannot be treeing we cannot be treeing you cannot be treeing they cannot be treeing
Perfect
I cannot have treed you cannot have treed she cannot have treed we cannot have treed you cannot have treed they cannot have treed
V-ing perfect
I cannot have been treeing you cannot have been treeing she cannot have been treeing we cannot have been treeing you cannot have been treeing they cannot have been treeing
Interrogative form
Simple form
can I tree? can you tree? can she tree? can we tree? can you tree? can they tree?
V-ing form
can I be treeing? can you be treeing? can she be treeing? can we be treeing? can you be treeing? can they be treeing?
Perfect
can I have treed? can you have treed? can she have treed? can we have treed? can you have treed? can they have treed?
V-ing perfect
can I have been treeing? can you have been treeing? can she have been treeing? can we have been treeing? can you have been treeing? can they have been treeing?
Interro-negative form
Simple form
can I not tree? can you not tree? can she not tree? can we not tree? can you not tree? can they not tree?
V-ing form
can I not be treeing? can you not be treeing? can she not be treeing? can we not be treeing? can you not be treeing? can they not be treeing?
Perfect
can I not have treed? can you not have treed? can she not have treed? can we not have treed? can you not have treed? can they not have treed?
V-ing perfect
can I not have been treeing? can you not have been treeing? can she not have been treeing? can we not have been treeing? can you not have been treeing? can they not have been treeing?