I could hello you could hello he could hello we could hello you could hello they could hello
V-ing form
I could be helloing you could be helloing he could be helloing we could be helloing you could be helloing they could be helloing
Perfect
I could have helloed you could have helloed he 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 he could have been helloing we could have been helloing you could have been helloing they could have been helloing
Negation
Simple form
I couldn't hello you couldn't hello he couldn't hello we couldn't hello you couldn't hello they couldn't hello
V-ing form
I couldn't be helloing you couldn't be helloing he couldn't be helloing we couldn't be helloing you couldn't be helloing they couldn't be helloing
Perfect
I couldn't have helloed you couldn't have helloed he couldn't have helloed we couldn't have helloed you couldn't have helloed they couldn't have helloed
V-ing perfect
I couldn't have been helloing you couldn't have been helloing he couldn't have been helloing we couldn't have been helloing you couldn't have been helloing they couldn't have been helloing
Interrogative form
Simple form
could I hello? could you hello? could he hello? could we hello? could you hello? could they hello?
V-ing form
could I be helloing? could you be helloing? could he be helloing? could we be helloing? could you be helloing? could they be helloing?
Perfect
could I have helloed? could you have helloed? could he 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 he have been helloing? could we have been helloing? could you have been helloing? could they have been helloing?
Interro-negative form
Simple form
couldn't I hello? couldn't you hello? couldn't he hello? couldn't we hello? couldn't you hello? couldn't they hello?
V-ing form
couldn't I be helloing? couldn't you be helloing? couldn't he be helloing? couldn't we be helloing? couldn't you be helloing? couldn't they be helloing?
Perfect
couldn't I have helloed? couldn't you have helloed? couldn't he have helloed? couldn't we have helloed? couldn't you have helloed? couldn't they have helloed?
V-ing perfect
couldn't I have been helloing? couldn't you have been helloing? couldn't he have been helloing? couldn't we have been helloing? couldn't you have been helloing? couldn't they have been helloing?