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