I can crumble you can crumble he can crumble we can crumble you can crumble they can crumble
V-ing form
I can be crumbling you can be crumbling he can be crumbling we can be crumbling you can be crumbling they can be crumbling
Perfect
I can have crumbled you can have crumbled he can have crumbled we can have crumbled you can have crumbled they can have crumbled
V-ing perfect
I can have been crumbling you can have been crumbling he can have been crumbling we can have been crumbling you can have been crumbling they can have been crumbling
Negation
Simple form
I can't crumble you can't crumble he can't crumble we can't crumble you can't crumble they can't crumble
V-ing form
I can't be crumbling you can't be crumbling he can't be crumbling we can't be crumbling you can't be crumbling they can't be crumbling
Perfect
I can't have crumbled you can't have crumbled he can't have crumbled we can't have crumbled you can't have crumbled they can't have crumbled
V-ing perfect
I can't have been crumbling you can't have been crumbling he can't have been crumbling we can't have been crumbling you can't have been crumbling they can't have been crumbling
Interrogative form
Simple form
can I crumble? can you crumble? can he crumble? can we crumble? can you crumble? can they crumble?
V-ing form
can I be crumbling? can you be crumbling? can he be crumbling? can we be crumbling? can you be crumbling? can they be crumbling?
Perfect
can I have crumbled? can you have crumbled? can he have crumbled? can we have crumbled? can you have crumbled? can they have crumbled?
V-ing perfect
can I have been crumbling? can you have been crumbling? can he have been crumbling? can we have been crumbling? can you have been crumbling? can they have been crumbling?
Interro-negative form
Simple form
can't I crumble? can't you crumble? can't he crumble? can't we crumble? can't you crumble? can't they crumble?
V-ing form
can't I be crumbling? can't you be crumbling? can't he be crumbling? can't we be crumbling? can't you be crumbling? can't they be crumbling?
Perfect
can't I have crumbled? can't you have crumbled? can't he have crumbled? can't we have crumbled? can't you have crumbled? can't they have crumbled?
V-ing perfect
can't I have been crumbling? can't you have been crumbling? can't he have been crumbling? can't we have been crumbling? can't you have been crumbling? can't they have been crumbling?