I could mystify you could mystify he could mystify we could mystify you could mystify they could mystify
V-ing form
I could be mystifying you could be mystifying he could be mystifying we could be mystifying you could be mystifying they could be mystifying
Perfect
I could have mystified you could have mystified he could have mystified we could have mystified you could have mystified they could have mystified
V-ing perfect
I could have been mystifying you could have been mystifying he could have been mystifying we could have been mystifying you could have been mystifying they could have been mystifying
Negation
Simple form
I could not mystify you could not mystify he could not mystify we could not mystify you could not mystify they could not mystify
V-ing form
I could not be mystifying you could not be mystifying he could not be mystifying we could not be mystifying you could not be mystifying they could not be mystifying
Perfect
I could not have mystified you could not have mystified he could not have mystified we could not have mystified you could not have mystified they could not have mystified
V-ing perfect
I could not have been mystifying you could not have been mystifying he could not have been mystifying we could not have been mystifying you could not have been mystifying they could not have been mystifying
Interrogative form
Simple form
could I mystify? could you mystify? could he mystify? could we mystify? could you mystify? could they mystify?
V-ing form
could I be mystifying? could you be mystifying? could he be mystifying? could we be mystifying? could you be mystifying? could they be mystifying?
Perfect
could I have mystified? could you have mystified? could he have mystified? could we have mystified? could you have mystified? could they have mystified?
V-ing perfect
could I have been mystifying? could you have been mystifying? could he have been mystifying? could we have been mystifying? could you have been mystifying? could they have been mystifying?
Interro-negative form
Simple form
could I not mystify? could you not mystify? could he not mystify? could we not mystify? could you not mystify? could they not mystify?
V-ing form
could I not be mystifying? could you not be mystifying? could he not be mystifying? could we not be mystifying? could you not be mystifying? could they not be mystifying?
Perfect
could I not have mystified? could you not have mystified? could he not have mystified? could we not have mystified? could you not have mystified? could they not have mystified?
V-ing perfect
could I not have been mystifying? could you not have been mystifying? could he not have been mystifying? could we not have been mystifying? could you not have been mystifying? could they not have been mystifying?