I can skate you can skate she can skate we can skate you can skate they can skate
V-ing form
I can be skating you can be skating she can be skating we can be skating you can be skating they can be skating
Perfect
I can have skated you can have skated she can have skated we can have skated you can have skated they can have skated
V-ing perfect
I can have been skating you can have been skating she can have been skating we can have been skating you can have been skating they can have been skating
Negation
Simple form
I cannot skate you cannot skate she cannot skate we cannot skate you cannot skate they cannot skate
V-ing form
I cannot be skating you cannot be skating she cannot be skating we cannot be skating you cannot be skating they cannot be skating
Perfect
I cannot have skated you cannot have skated she cannot have skated we cannot have skated you cannot have skated they cannot have skated
V-ing perfect
I cannot have been skating you cannot have been skating she cannot have been skating we cannot have been skating you cannot have been skating they cannot have been skating
Interrogative form
Simple form
can I skate? can you skate? can she skate? can we skate? can you skate? can they skate?
V-ing form
can I be skating? can you be skating? can she be skating? can we be skating? can you be skating? can they be skating?
Perfect
can I have skated? can you have skated? can she have skated? can we have skated? can you have skated? can they have skated?
V-ing perfect
can I have been skating? can you have been skating? can she have been skating? can we have been skating? can you have been skating? can they have been skating?
Interro-negative form
Simple form
can I not skate? can you not skate? can she not skate? can we not skate? can you not skate? can they not skate?
V-ing form
can I not be skating? can you not be skating? can she not be skating? can we not be skating? can you not be skating? can they not be skating?
Perfect
can I not have skated? can you not have skated? can she not have skated? can we not have skated? can you not have skated? can they not have skated?
V-ing perfect
can I not have been skating? can you not have been skating? can she not have been skating? can we not have been skating? can you not have been skating? can they not have been skating?