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 couldn't append you couldn't append he couldn't append we couldn't append you couldn't append they couldn't append
V-ing form
I couldn't be appending you couldn't be appending he couldn't be appending we couldn't be appending you couldn't be appending they couldn't be appending
Perfect
I couldn't have appended you couldn't have appended he couldn't have appended we couldn't have appended you couldn't have appended they couldn't have appended
V-ing perfect
I couldn't have been appending you couldn't have been appending he couldn't have been appending we couldn't have been appending you couldn't have been appending they couldn't 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
couldn't I append? couldn't you append? couldn't he append? couldn't we append? couldn't you append? couldn't they append?
V-ing form
couldn't I be appending? couldn't you be appending? couldn't he be appending? couldn't we be appending? couldn't you be appending? couldn't they be appending?
Perfect
couldn't I have appended? couldn't you have appended? couldn't he have appended? couldn't we have appended? couldn't you have appended? couldn't they have appended?
V-ing perfect
couldn't I have been appending? couldn't you have been appending? couldn't he have been appending? couldn't we have been appending? couldn't you have been appending? couldn't they have been appending?