I can lack you can lack he can lack we can lack you can lack they can lack
V-ing form
I can be lacking you can be lacking he can be lacking we can be lacking you can be lacking they can be lacking
Perfect
I can have lacked you can have lacked he can have lacked we can have lacked you can have lacked they can have lacked
V-ing perfect
I can have been lacking you can have been lacking he can have been lacking we can have been lacking you can have been lacking they can have been lacking
Negation
Simple form
I can't lack you can't lack he can't lack we can't lack you can't lack they can't lack
V-ing form
I can't be lacking you can't be lacking he can't be lacking we can't be lacking you can't be lacking they can't be lacking
Perfect
I can't have lacked you can't have lacked he can't have lacked we can't have lacked you can't have lacked they can't have lacked
V-ing perfect
I can't have been lacking you can't have been lacking he can't have been lacking we can't have been lacking you can't have been lacking they can't have been lacking
Interrogative form
Simple form
can I lack? can you lack? can he lack? can we lack? can you lack? can they lack?
V-ing form
can I be lacking? can you be lacking? can he be lacking? can we be lacking? can you be lacking? can they be lacking?
Perfect
can I have lacked? can you have lacked? can he have lacked? can we have lacked? can you have lacked? can they have lacked?
V-ing perfect
can I have been lacking? can you have been lacking? can he have been lacking? can we have been lacking? can you have been lacking? can they have been lacking?
Interro-negative form
Simple form
can't I lack? can't you lack? can't he lack? can't we lack? can't you lack? can't they lack?
V-ing form
can't I be lacking? can't you be lacking? can't he be lacking? can't we be lacking? can't you be lacking? can't they be lacking?
Perfect
can't I have lacked? can't you have lacked? can't he have lacked? can't we have lacked? can't you have lacked? can't they have lacked?
V-ing perfect
can't I have been lacking? can't you have been lacking? can't he have been lacking? can't we have been lacking? can't you have been lacking? can't they have been lacking?