I could inquire you could inquire she could inquire we could inquire you could inquire they could inquire
V-ing form
I could be inquiring you could be inquiring she could be inquiring we could be inquiring you could be inquiring they could be inquiring
Perfect
I could have inquired you could have inquired she could have inquired we could have inquired you could have inquired they could have inquired
V-ing perfect
I could have been inquiring you could have been inquiring she could have been inquiring we could have been inquiring you could have been inquiring they could have been inquiring
Negation
Simple form
I could not inquire you could not inquire she could not inquire we could not inquire you could not inquire they could not inquire
V-ing form
I could not be inquiring you could not be inquiring she could not be inquiring we could not be inquiring you could not be inquiring they could not be inquiring
Perfect
I could not have inquired you could not have inquired she could not have inquired we could not have inquired you could not have inquired they could not have inquired
V-ing perfect
I could not have been inquiring you could not have been inquiring she could not have been inquiring we could not have been inquiring you could not have been inquiring they could not have been inquiring
Interrogative form
Simple form
could I inquire? could you inquire? could she inquire? could we inquire? could you inquire? could they inquire?
V-ing form
could I be inquiring? could you be inquiring? could she be inquiring? could we be inquiring? could you be inquiring? could they be inquiring?
Perfect
could I have inquired? could you have inquired? could she have inquired? could we have inquired? could you have inquired? could they have inquired?
V-ing perfect
could I have been inquiring? could you have been inquiring? could she have been inquiring? could we have been inquiring? could you have been inquiring? could they have been inquiring?
Interro-negative form
Simple form
could I not inquire? could you not inquire? could she not inquire? could we not inquire? could you not inquire? could they not inquire?
V-ing form
could I not be inquiring? could you not be inquiring? could she not be inquiring? could we not be inquiring? could you not be inquiring? could they not be inquiring?
Perfect
could I not have inquired? could you not have inquired? could she not have inquired? could we not have inquired? could you not have inquired? could they not have inquired?
V-ing perfect
could I not have been inquiring? could you not have been inquiring? could she not have been inquiring? could we not have been inquiring? could you not have been inquiring? could they not have been inquiring?