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