I could cross-check you could cross-check he could cross-check we could cross-check you could cross-check they could cross-check
V-ing form
I could be cross-checking you could be cross-checking he could be cross-checking we could be cross-checking you could be cross-checking they could be cross-checking
Perfect
I could have cross-checked you could have cross-checked he could have cross-checked we could have cross-checked you could have cross-checked they could have cross-checked
V-ing perfect
I could have been cross-checking you could have been cross-checking he could have been cross-checking we could have been cross-checking you could have been cross-checking they could have been cross-checking
Negation
Simple form
I couldn't cross-check you couldn't cross-check he couldn't cross-check we couldn't cross-check you couldn't cross-check they couldn't cross-check
V-ing form
I couldn't be cross-checking you couldn't be cross-checking he couldn't be cross-checking we couldn't be cross-checking you couldn't be cross-checking they couldn't be cross-checking
Perfect
I couldn't have cross-checked you couldn't have cross-checked he couldn't have cross-checked we couldn't have cross-checked you couldn't have cross-checked they couldn't have cross-checked
V-ing perfect
I couldn't have been cross-checking you couldn't have been cross-checking he couldn't have been cross-checking we couldn't have been cross-checking you couldn't have been cross-checking they couldn't have been cross-checking
Interrogative form
Simple form
could I cross-check? could you cross-check? could he cross-check? could we cross-check? could you cross-check? could they cross-check?
V-ing form
could I be cross-checking? could you be cross-checking? could he be cross-checking? could we be cross-checking? could you be cross-checking? could they be cross-checking?
Perfect
could I have cross-checked? could you have cross-checked? could he have cross-checked? could we have cross-checked? could you have cross-checked? could they have cross-checked?
V-ing perfect
could I have been cross-checking? could you have been cross-checking? could he have been cross-checking? could we have been cross-checking? could you have been cross-checking? could they have been cross-checking?
Interro-negative form
Simple form
couldn't I cross-check? couldn't you cross-check? couldn't he cross-check? couldn't we cross-check? couldn't you cross-check? couldn't they cross-check?
V-ing form
couldn't I be cross-checking? couldn't you be cross-checking? couldn't he be cross-checking? couldn't we be cross-checking? couldn't you be cross-checking? couldn't they be cross-checking?
Perfect
couldn't I have cross-checked? couldn't you have cross-checked? couldn't he have cross-checked? couldn't we have cross-checked? couldn't you have cross-checked? couldn't they have cross-checked?
V-ing perfect
couldn't I have been cross-checking? couldn't you have been cross-checking? couldn't he have been cross-checking? couldn't we have been cross-checking? couldn't you have been cross-checking? couldn't they have been cross-checking?