I can thumbtack you can thumbtack he can thumbtack we can thumbtack you can thumbtack they can thumbtack
V-ing form
I can be thumbtacking you can be thumbtacking he can be thumbtacking we can be thumbtacking you can be thumbtacking they can be thumbtacking
Perfect
I can have thumbtacked you can have thumbtacked he can have thumbtacked we can have thumbtacked you can have thumbtacked they can have thumbtacked
V-ing perfect
I can have been thumbtacking you can have been thumbtacking he can have been thumbtacking we can have been thumbtacking you can have been thumbtacking they can have been thumbtacking
Negation
Simple form
I cannot thumbtack you cannot thumbtack he cannot thumbtack we cannot thumbtack you cannot thumbtack they cannot thumbtack
V-ing form
I cannot be thumbtacking you cannot be thumbtacking he cannot be thumbtacking we cannot be thumbtacking you cannot be thumbtacking they cannot be thumbtacking
Perfect
I cannot have thumbtacked you cannot have thumbtacked he cannot have thumbtacked we cannot have thumbtacked you cannot have thumbtacked they cannot have thumbtacked
V-ing perfect
I cannot have been thumbtacking you cannot have been thumbtacking he cannot have been thumbtacking we cannot have been thumbtacking you cannot have been thumbtacking they cannot have been thumbtacking
Interrogative form
Simple form
can I thumbtack? can you thumbtack? can he thumbtack? can we thumbtack? can you thumbtack? can they thumbtack?
V-ing form
can I be thumbtacking? can you be thumbtacking? can he be thumbtacking? can we be thumbtacking? can you be thumbtacking? can they be thumbtacking?
Perfect
can I have thumbtacked? can you have thumbtacked? can he have thumbtacked? can we have thumbtacked? can you have thumbtacked? can they have thumbtacked?
V-ing perfect
can I have been thumbtacking? can you have been thumbtacking? can he have been thumbtacking? can we have been thumbtacking? can you have been thumbtacking? can they have been thumbtacking?
Interro-negative form
Simple form
can I not thumbtack? can you not thumbtack? can he not thumbtack? can we not thumbtack? can you not thumbtack? can they not thumbtack?
V-ing form
can I not be thumbtacking? can you not be thumbtacking? can he not be thumbtacking? can we not be thumbtacking? can you not be thumbtacking? can they not be thumbtacking?
Perfect
can I not have thumbtacked? can you not have thumbtacked? can he not have thumbtacked? can we not have thumbtacked? can you not have thumbtacked? can they not have thumbtacked?
V-ing perfect
can I not have been thumbtacking? can you not have been thumbtacking? can he not have been thumbtacking? can we not have been thumbtacking? can you not have been thumbtacking? can they not have been thumbtacking?