I can enter you can enter he can enter we can enter you can enter they can enter
V-ing form
I can be entering you can be entering he can be entering we can be entering you can be entering they can be entering
Perfect
I can have entered you can have entered he can have entered we can have entered you can have entered they can have entered
V-ing perfect
I can have been entering you can have been entering he can have been entering we can have been entering you can have been entering they can have been entering
Negation
Simple form
I can't enter you can't enter he can't enter we can't enter you can't enter they can't enter
V-ing form
I can't be entering you can't be entering he can't be entering we can't be entering you can't be entering they can't be entering
Perfect
I can't have entered you can't have entered he can't have entered we can't have entered you can't have entered they can't have entered
V-ing perfect
I can't have been entering you can't have been entering he can't have been entering we can't have been entering you can't have been entering they can't have been entering
Interrogative form
Simple form
can I enter? can you enter? can he enter? can we enter? can you enter? can they enter?
V-ing form
can I be entering? can you be entering? can he be entering? can we be entering? can you be entering? can they be entering?
Perfect
can I have entered? can you have entered? can he have entered? can we have entered? can you have entered? can they have entered?
V-ing perfect
can I have been entering? can you have been entering? can he have been entering? can we have been entering? can you have been entering? can they have been entering?
Interro-negative form
Simple form
can't I enter? can't you enter? can't he enter? can't we enter? can't you enter? can't they enter?
V-ing form
can't I be entering? can't you be entering? can't he be entering? can't we be entering? can't you be entering? can't they be entering?
Perfect
can't I have entered? can't you have entered? can't he have entered? can't we have entered? can't you have entered? can't they have entered?
V-ing perfect
can't I have been entering? can't you have been entering? can't he have been entering? can't we have been entering? can't you have been entering? can't they have been entering?