English verb conjugation
COULD CLUSTER

Regular verb: cluster - clustered - clustered

Affirmation

Simple form	V-ing form
I could cluster you could cluster he could cluster we could cluster you could cluster they could cluster	I could be clustering you could be clustering he could be clustering we could be clustering you could be clustering they could be clustering
Perfect	V-ing perfect
I could have clustered you could have clustered he could have clustered we could have clustered you could have clustered they could have clustered	I could have been clustering you could have been clustering he could have been clustering we could have been clustering you could have been clustering they could have been clustering

Negation

Simple form	V-ing form
I couldn't cluster you couldn't cluster he couldn't cluster we couldn't cluster you couldn't cluster they couldn't cluster	I couldn't be clustering you couldn't be clustering he couldn't be clustering we couldn't be clustering you couldn't be clustering they couldn't be clustering
Perfect	V-ing perfect
I couldn't have clustered you couldn't have clustered he couldn't have clustered we couldn't have clustered you couldn't have clustered they couldn't have clustered	I couldn't have been clustering you couldn't have been clustering he couldn't have been clustering we couldn't have been clustering you couldn't have been clustering they couldn't have been clustering

Interrogative form

Simple form	V-ing form
could I cluster? could you cluster? could he cluster? could we cluster? could you cluster? could they cluster?	could I be clustering? could you be clustering? could he be clustering? could we be clustering? could you be clustering? could they be clustering?
Perfect	V-ing perfect
could I have clustered? could you have clustered? could he have clustered? could we have clustered? could you have clustered? could they have clustered?	could I have been clustering? could you have been clustering? could he have been clustering? could we have been clustering? could you have been clustering? could they have been clustering?

Interro-negative form

Simple form	V-ing form
couldn't I cluster? couldn't you cluster? couldn't he cluster? couldn't we cluster? couldn't you cluster? couldn't they cluster?	couldn't I be clustering? couldn't you be clustering? couldn't he be clustering? couldn't we be clustering? couldn't you be clustering? couldn't they be clustering?
Perfect	V-ing perfect
couldn't I have clustered? couldn't you have clustered? couldn't he have clustered? couldn't we have clustered? couldn't you have clustered? couldn't they have clustered?	couldn't I have been clustering? couldn't you have been clustering? couldn't he have been clustering? couldn't we have been clustering? couldn't you have been clustering? couldn't they have been clustering?