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