I could differentiate you could differentiate he could differentiate we could differentiate you could differentiate they could differentiate
V-ing form
I could be differentiating you could be differentiating he could be differentiating we could be differentiating you could be differentiating they could be differentiating
Perfect
I could have differentiated you could have differentiated he could have differentiated we could have differentiated you could have differentiated they could have differentiated
V-ing perfect
I could have been differentiating you could have been differentiating he could have been differentiating we could have been differentiating you could have been differentiating they could have been differentiating
Negation
Simple form
I could not differentiate you could not differentiate he could not differentiate we could not differentiate you could not differentiate they could not differentiate
V-ing form
I could not be differentiating you could not be differentiating he could not be differentiating we could not be differentiating you could not be differentiating they could not be differentiating
Perfect
I could not have differentiated you could not have differentiated he could not have differentiated we could not have differentiated you could not have differentiated they could not have differentiated
V-ing perfect
I could not have been differentiating you could not have been differentiating he could not have been differentiating we could not have been differentiating you could not have been differentiating they could not have been differentiating
Interrogative form
Simple form
could I differentiate? could you differentiate? could he differentiate? could we differentiate? could you differentiate? could they differentiate?
V-ing form
could I be differentiating? could you be differentiating? could he be differentiating? could we be differentiating? could you be differentiating? could they be differentiating?
Perfect
could I have differentiated? could you have differentiated? could he have differentiated? could we have differentiated? could you have differentiated? could they have differentiated?
V-ing perfect
could I have been differentiating? could you have been differentiating? could he have been differentiating? could we have been differentiating? could you have been differentiating? could they have been differentiating?
Interro-negative form
Simple form
could I not differentiate? could you not differentiate? could he not differentiate? could we not differentiate? could you not differentiate? could they not differentiate?
V-ing form
could I not be differentiating? could you not be differentiating? could he not be differentiating? could we not be differentiating? could you not be differentiating? could they not be differentiating?
Perfect
could I not have differentiated? could you not have differentiated? could he not have differentiated? could we not have differentiated? could you not have differentiated? could they not have differentiated?
V-ing perfect
could I not have been differentiating? could you not have been differentiating? could he not have been differentiating? could we not have been differentiating? could you not have been differentiating? could they not have been differentiating?