English verb conjugation
CAN CLACK

Regular verb: clack - clacked - clacked

Affirmation

Simple form	V-ing form
I can clack you can clack he can clack we can clack you can clack they can clack	I can be clacking you can be clacking he can be clacking we can be clacking you can be clacking they can be clacking
Perfect	V-ing perfect
I can have clacked you can have clacked he can have clacked we can have clacked you can have clacked they can have clacked	I can have been clacking you can have been clacking he can have been clacking we can have been clacking you can have been clacking they can have been clacking

Negation

Simple form	V-ing form
I cannot clack you cannot clack he cannot clack we cannot clack you cannot clack they cannot clack	I cannot be clacking you cannot be clacking he cannot be clacking we cannot be clacking you cannot be clacking they cannot be clacking
Perfect	V-ing perfect
I cannot have clacked you cannot have clacked he cannot have clacked we cannot have clacked you cannot have clacked they cannot have clacked	I cannot have been clacking you cannot have been clacking he cannot have been clacking we cannot have been clacking you cannot have been clacking they cannot have been clacking

Interrogative form

Simple form	V-ing form
can I clack? can you clack? can he clack? can we clack? can you clack? can they clack?	can I be clacking? can you be clacking? can he be clacking? can we be clacking? can you be clacking? can they be clacking?
Perfect	V-ing perfect
can I have clacked? can you have clacked? can he have clacked? can we have clacked? can you have clacked? can they have clacked?	can I have been clacking? can you have been clacking? can he have been clacking? can we have been clacking? can you have been clacking? can they have been clacking?

Interro-negative form

Simple form	V-ing form
can I not clack? can you not clack? can he not clack? can we not clack? can you not clack? can they not clack?	can I not be clacking? can you not be clacking? can he not be clacking? can we not be clacking? can you not be clacking? can they not be clacking?
Perfect	V-ing perfect
can I not have clacked? can you not have clacked? can he not have clacked? can we not have clacked? can you not have clacked? can they not have clacked?	can I not have been clacking? can you not have been clacking? can he not have been clacking? can we not have been clacking? can you not have been clacking? can they not have been clacking?