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