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 cannot collapse you cannot collapse he cannot collapse we cannot collapse you cannot collapse they cannot collapse
V-ing form
I cannot be collapsing you cannot be collapsing he cannot be collapsing we cannot be collapsing you cannot be collapsing they cannot be collapsing
Perfect
I cannot have collapsed you cannot have collapsed he cannot have collapsed we cannot have collapsed you cannot have collapsed they cannot have collapsed
V-ing perfect
I cannot have been collapsing you cannot have been collapsing he cannot have been collapsing we cannot have been collapsing you cannot have been collapsing they cannot 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 I not collapse? can you not collapse? can he not collapse? can we not collapse? can you not collapse? can they not collapse?
V-ing form
can I not be collapsing? can you not be collapsing? can he not be collapsing? can we not be collapsing? can you not be collapsing? can they not be collapsing?
Perfect
can I not have collapsed? can you not have collapsed? can he not have collapsed? can we not have collapsed? can you not have collapsed? can they not have collapsed?
V-ing perfect
can I not have been collapsing? can you not have been collapsing? can he not have been collapsing? can we not have been collapsing? can you not have been collapsing? can they not have been collapsing?