I can collapse you can collapse he can collapse we can collapse you can collapse they can collapse
V-ing form
I can be collapsing you can be collapsing he can be collapsing we can be collapsing you can be collapsing they can be collapsing
Perfect
I can have collapsed you can have collapsed he can have collapsed we can have collapsed you can have collapsed they can have collapsed
V-ing perfect
I can have been collapsing you can have been collapsing he can have been collapsing we can have been collapsing you can have been collapsing they can have been collapsing
Negation
Simple form
I can't collapse you can't collapse he can't collapse we can't collapse you can't collapse they can't collapse
V-ing form
I can't be collapsing you can't be collapsing he can't be collapsing we can't be collapsing you can't be collapsing they can't be collapsing
Perfect
I can't have collapsed you can't have collapsed he can't have collapsed we can't have collapsed you can't have collapsed they can't have collapsed
V-ing perfect
I can't have been collapsing you can't have been collapsing he can't have been collapsing we can't have been collapsing you can't have been collapsing they can't have been collapsing
Interrogative form
Simple form
can I collapse? can you collapse? can he collapse? can we collapse? can you collapse? can they collapse?
V-ing form
can I be collapsing? can you be collapsing? can he be collapsing? can we be collapsing? can you be collapsing? can they be collapsing?
Perfect
can I have collapsed? can you have collapsed? can he have collapsed? can we have collapsed? can you have collapsed? can they have collapsed?
V-ing perfect
can I have been collapsing? can you have been collapsing? can he have been collapsing? can we have been collapsing? can you have been collapsing? can they have been collapsing?
Interro-negative form
Simple form
can't I collapse? can't you collapse? can't he collapse? can't we collapse? can't you collapse? can't they collapse?
V-ing form
can't I be collapsing? can't you be collapsing? can't he be collapsing? can't we be collapsing? can't you be collapsing? can't they be collapsing?
Perfect
can't I have collapsed? can't you have collapsed? can't he have collapsed? can't we have collapsed? can't you have collapsed? can't they have collapsed?
V-ing perfect
can't I have been collapsing? can't you have been collapsing? can't he have been collapsing? can't we have been collapsing? can't you have been collapsing? can't they have been collapsing?