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 can't inquire you can't inquire he can't inquire we can't inquire you can't inquire they can't inquire
V-ing form
I can't be inquiring you can't be inquiring he can't be inquiring we can't be inquiring you can't be inquiring they can't be inquiring
Perfect
I can't have inquired you can't have inquired he can't have inquired we can't have inquired you can't have inquired they can't have inquired
V-ing perfect
I can't have been inquiring you can't have been inquiring he can't have been inquiring we can't have been inquiring you can't have been inquiring they can't 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't I inquire? can't you inquire? can't he inquire? can't we inquire? can't you inquire? can't they inquire?
V-ing form
can't I be inquiring? can't you be inquiring? can't he be inquiring? can't we be inquiring? can't you be inquiring? can't they be inquiring?
Perfect
can't I have inquired? can't you have inquired? can't he have inquired? can't we have inquired? can't you have inquired? can't they have inquired?
V-ing perfect
can't I have been inquiring? can't you have been inquiring? can't he have been inquiring? can't we have been inquiring? can't you have been inquiring? can't they have been inquiring?