I could hello you could hello she could hello we could hello you could hello they could hello
V-ing form
I could be helloing you could be helloing she could be helloing we could be helloing you could be helloing they could be helloing
Perfect
I could have helloed you could have helloed she could have helloed we could have helloed you could have helloed they could have helloed
V-ing perfect
I could have been helloing you could have been helloing she could have been helloing we could have been helloing you could have been helloing they could have been helloing
Negation
Simple form
I could not hello you could not hello she could not hello we could not hello you could not hello they could not hello
V-ing form
I could not be helloing you could not be helloing she could not be helloing we could not be helloing you could not be helloing they could not be helloing
Perfect
I could not have helloed you could not have helloed she could not have helloed we could not have helloed you could not have helloed they could not have helloed
V-ing perfect
I could not have been helloing you could not have been helloing she could not have been helloing we could not have been helloing you could not have been helloing they could not have been helloing
Interrogative form
Simple form
could I hello? could you hello? could she hello? could we hello? could you hello? could they hello?
V-ing form
could I be helloing? could you be helloing? could she be helloing? could we be helloing? could you be helloing? could they be helloing?
Perfect
could I have helloed? could you have helloed? could she have helloed? could we have helloed? could you have helloed? could they have helloed?
V-ing perfect
could I have been helloing? could you have been helloing? could she have been helloing? could we have been helloing? could you have been helloing? could they have been helloing?
Interro-negative form
Simple form
could I not hello? could you not hello? could she not hello? could we not hello? could you not hello? could they not hello?
V-ing form
could I not be helloing? could you not be helloing? could she not be helloing? could we not be helloing? could you not be helloing? could they not be helloing?
Perfect
could I not have helloed? could you not have helloed? could she not have helloed? could we not have helloed? could you not have helloed? could they not have helloed?
V-ing perfect
could I not have been helloing? could you not have been helloing? could she not have been helloing? could we not have been helloing? could you not have been helloing? could they not have been helloing?