I could append you could append he could append we could append you could append they could append
V-ing form
I could be appending you could be appending he could be appending we could be appending you could be appending they could be appending
Perfect
I could have appended you could have appended he could have appended we could have appended you could have appended they could have appended
V-ing perfect
I could have been appending you could have been appending he could have been appending we could have been appending you could have been appending they could have been appending
Negation
Simple form
I could not append you could not append he could not append we could not append you could not append they could not append
V-ing form
I could not be appending you could not be appending he could not be appending we could not be appending you could not be appending they could not be appending
Perfect
I could not have appended you could not have appended he could not have appended we could not have appended you could not have appended they could not have appended
V-ing perfect
I could not have been appending you could not have been appending he could not have been appending we could not have been appending you could not have been appending they could not have been appending
Interrogative form
Simple form
could I append? could you append? could he append? could we append? could you append? could they append?
V-ing form
could I be appending? could you be appending? could he be appending? could we be appending? could you be appending? could they be appending?
Perfect
could I have appended? could you have appended? could he have appended? could we have appended? could you have appended? could they have appended?
V-ing perfect
could I have been appending? could you have been appending? could he have been appending? could we have been appending? could you have been appending? could they have been appending?
Interro-negative form
Simple form
could I not append? could you not append? could he not append? could we not append? could you not append? could they not append?
V-ing form
could I not be appending? could you not be appending? could he not be appending? could we not be appending? could you not be appending? could they not be appending?
Perfect
could I not have appended? could you not have appended? could he not have appended? could we not have appended? could you not have appended? could they not have appended?
V-ing perfect
could I not have been appending? could you not have been appending? could he not have been appending? could we not have been appending? could you not have been appending? could they not have been appending?