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 mustn't thumbtack you mustn't thumbtack he mustn't thumbtack we mustn't thumbtack you mustn't thumbtack they mustn't thumbtack
V-ing form
I mustn't be thumbtacking you mustn't be thumbtacking he mustn't be thumbtacking we mustn't be thumbtacking you mustn't be thumbtacking they mustn't be thumbtacking
Perfect
I mustn't have thumbtacked you mustn't have thumbtacked he mustn't have thumbtacked we mustn't have thumbtacked you mustn't have thumbtacked they mustn't have thumbtacked
V-ing perfect
I mustn't have been thumbtacking you mustn't have been thumbtacking he mustn't have been thumbtacking we mustn't have been thumbtacking you mustn't have been thumbtacking they mustn't 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
mustn't I thumbtack? mustn't you thumbtack? mustn't he thumbtack? mustn't we thumbtack? mustn't you thumbtack? mustn't they thumbtack?
V-ing form
mustn't I be thumbtacking? mustn't you be thumbtacking? mustn't he be thumbtacking? mustn't we be thumbtacking? mustn't you be thumbtacking? mustn't they be thumbtacking?
Perfect
mustn't I have thumbtacked? mustn't you have thumbtacked? mustn't he have thumbtacked? mustn't we have thumbtacked? mustn't you have thumbtacked? mustn't they have thumbtacked?
V-ing perfect
mustn't I have been thumbtacking? mustn't you have been thumbtacking? mustn't he have been thumbtacking? mustn't we have been thumbtacking? mustn't you have been thumbtacking? mustn't they have been thumbtacking?