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