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 cannot enter you cannot enter he cannot enter we cannot enter you cannot enter they cannot enter
V-ing form
I cannot be entering you cannot be entering he cannot be entering we cannot be entering you cannot be entering they cannot be entering
Perfect
I cannot have entered you cannot have entered he cannot have entered we cannot have entered you cannot have entered they cannot have entered
V-ing perfect
I cannot have been entering you cannot have been entering he cannot have been entering we cannot have been entering you cannot have been entering they cannot 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 I not enter? can you not enter? can he not enter? can we not enter? can you not enter? can they not enter?
V-ing form
can I not be entering? can you not be entering? can he not be entering? can we not be entering? can you not be entering? can they not be entering?
Perfect
can I not have entered? can you not have entered? can he not have entered? can we not have entered? can you not have entered? can they not have entered?
V-ing perfect
can I not have been entering? can you not have been entering? can he not have been entering? can we not have been entering? can you not have been entering? can they not have been entering?