I can extend you can extend she can extend we can extend you can extend they can extend
V-ing form
I can be extending you can be extending she can be extending we can be extending you can be extending they can be extending
Perfect
I can have extended you can have extended she can have extended we can have extended you can have extended they can have extended
V-ing perfect
I can have been extending you can have been extending she can have been extending we can have been extending you can have been extending they can have been extending
Negation
Simple form
I can't extend you can't extend she can't extend we can't extend you can't extend they can't extend
V-ing form
I can't be extending you can't be extending she can't be extending we can't be extending you can't be extending they can't be extending
Perfect
I can't have extended you can't have extended she can't have extended we can't have extended you can't have extended they can't have extended
V-ing perfect
I can't have been extending you can't have been extending she can't have been extending we can't have been extending you can't have been extending they can't have been extending
Interrogative form
Simple form
can I extend? can you extend? can she extend? can we extend? can you extend? can they extend?
V-ing form
can I be extending? can you be extending? can she be extending? can we be extending? can you be extending? can they be extending?
Perfect
can I have extended? can you have extended? can she have extended? can we have extended? can you have extended? can they have extended?
V-ing perfect
can I have been extending? can you have been extending? can she have been extending? can we have been extending? can you have been extending? can they have been extending?
Interro-negative form
Simple form
can't I extend? can't you extend? can't she extend? can't we extend? can't you extend? can't they extend?
V-ing form
can't I be extending? can't you be extending? can't she be extending? can't we be extending? can't you be extending? can't they be extending?
Perfect
can't I have extended? can't you have extended? can't she have extended? can't we have extended? can't you have extended? can't they have extended?
V-ing perfect
can't I have been extending? can't you have been extending? can't she have been extending? can't we have been extending? can't you have been extending? can't they have been extending?