I can sit you can sit she can sit we can sit you can sit they can sit
V-ing form
I can be sitting you can be sitting she can be sitting we can be sitting you can be sitting they can be sitting
Perfect
I can have sat you can have sat she can have sat we can have sat you can have sat they can have sat
V-ing perfect
I can have been sitting you can have been sitting she can have been sitting we can have been sitting you can have been sitting they can have been sitting
Negation
Simple form
I can't sit you can't sit she can't sit we can't sit you can't sit they can't sit
V-ing form
I can't be sitting you can't be sitting she can't be sitting we can't be sitting you can't be sitting they can't be sitting
Perfect
I can't have sat you can't have sat she can't have sat we can't have sat you can't have sat they can't have sat
V-ing perfect
I can't have been sitting you can't have been sitting she can't have been sitting we can't have been sitting you can't have been sitting they can't have been sitting
Interrogative form
Simple form
can I sit? can you sit? can she sit? can we sit? can you sit? can they sit?
V-ing form
can I be sitting? can you be sitting? can she be sitting? can we be sitting? can you be sitting? can they be sitting?
Perfect
can I have sat? can you have sat? can she have sat? can we have sat? can you have sat? can they have sat?
V-ing perfect
can I have been sitting? can you have been sitting? can she have been sitting? can we have been sitting? can you have been sitting? can they have been sitting?
Interro-negative form
Simple form
can't I sit? can't you sit? can't she sit? can't we sit? can't you sit? can't they sit?
V-ing form
can't I be sitting? can't you be sitting? can't she be sitting? can't we be sitting? can't you be sitting? can't they be sitting?
Perfect
can't I have sat? can't you have sat? can't she have sat? can't we have sat? can't you have sat? can't they have sat?
V-ing perfect
can't I have been sitting? can't you have been sitting? can't she have been sitting? can't we have been sitting? can't you have been sitting? can't they have been sitting?