What does "—it's just not done" mean here It means that no one in Thailand ______.

A．In Bulgaria, you are likely to be left thirsty if you nod when offered a drink.
B．In Bulgaria, nodding one's head is a sign of agreement or acceptance.
C．Your Arabic host won't refill your drinking vessel if you don't insist.
D．In countries on the Arabian Peninsula you must shake your head to signify "yes".

A．Master the language of that country.
B．Speak less and watch more.
C．Wait and see unless you are sure of success.
D．Learn more about the culture as well as ensuring a command of the language.