I can assist you can assist he can assist we can assist you can assist they can assist
V-ing form
I can be assisting you can be assisting he can be assisting we can be assisting you can be assisting they can be assisting
Perfect
I can have assisted you can have assisted he can have assisted we can have assisted you can have assisted they can have assisted
V-ing perfect
I can have been assisting you can have been assisting he can have been assisting we can have been assisting you can have been assisting they can have been assisting
Negation
Simple form
I cannot assist you cannot assist he cannot assist we cannot assist you cannot assist they cannot assist
V-ing form
I cannot be assisting you cannot be assisting he cannot be assisting we cannot be assisting you cannot be assisting they cannot be assisting
Perfect
I cannot have assisted you cannot have assisted he cannot have assisted we cannot have assisted you cannot have assisted they cannot have assisted
V-ing perfect
I cannot have been assisting you cannot have been assisting he cannot have been assisting we cannot have been assisting you cannot have been assisting they cannot have been assisting
Interrogative form
Simple form
can I assist? can you assist? can he assist? can we assist? can you assist? can they assist?
V-ing form
can I be assisting? can you be assisting? can he be assisting? can we be assisting? can you be assisting? can they be assisting?
Perfect
can I have assisted? can you have assisted? can he have assisted? can we have assisted? can you have assisted? can they have assisted?
V-ing perfect
can I have been assisting? can you have been assisting? can he have been assisting? can we have been assisting? can you have been assisting? can they have been assisting?
Interro-negative form
Simple form
can I not assist? can you not assist? can he not assist? can we not assist? can you not assist? can they not assist?
V-ing form
can I not be assisting? can you not be assisting? can he not be assisting? can we not be assisting? can you not be assisting? can they not be assisting?
Perfect
can I not have assisted? can you not have assisted? can he not have assisted? can we not have assisted? can you not have assisted? can they not have assisted?
V-ing perfect
can I not have been assisting? can you not have been assisting? can he not have been assisting? can we not have been assisting? can you not have been assisting? can they not have been assisting?