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