I can skate you can skate he can skate we can skate you can skate they can skate
V-ing form
I can be skating you can be skating he can be skating we can be skating you can be skating they can be skating
Perfect
I can have skated you can have skated he 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 he can have been skating we can have been skating you can have been skating they can have been skating
Negation
Simple form
I can't skate you can't skate he can't skate we can't skate you can't skate they can't skate
V-ing form
I can't be skating you can't be skating he can't be skating we can't be skating you can't be skating they can't be skating
Perfect
I can't have skated you can't have skated he can't have skated we can't have skated you can't have skated they can't have skated
V-ing perfect
I can't have been skating you can't have been skating he can't have been skating we can't have been skating you can't have been skating they can't have been skating
Interrogative form
Simple form
can I skate? can you skate? can he skate? can we skate? can you skate? can they skate?
V-ing form
can I be skating? can you be skating? can he be skating? can we be skating? can you be skating? can they be skating?
Perfect
can I have skated? can you have skated? can he 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 he have been skating? can we have been skating? can you have been skating? can they have been skating?
Interro-negative form
Simple form
can't I skate? can't you skate? can't he skate? can't we skate? can't you skate? can't they skate?
V-ing form
can't I be skating? can't you be skating? can't he be skating? can't we be skating? can't you be skating? can't they be skating?
Perfect
can't I have skated? can't you have skated? can't he have skated? can't we have skated? can't you have skated? can't they have skated?
V-ing perfect
can't I have been skating? can't you have been skating? can't he have been skating? can't we have been skating? can't you have been skating? can't they have been skating?