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