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