The napkin _________ be left on the chair.

Choose the letter A, B, C or D to answer these following questions
HOW TO USE NAPKINS IN AN AMERICAN RESTAURANT?
As soon as you are seated, remove the napkin from your place setting, unfold it, and put it in your lap. Do not shake it open. At some very formal restaurants, the waiter may do this for the diners, but it is not inappropriate to place your own napkin in your lap, even when this is the case. The napkin rests on the lap till the end of the meal. Do not clean the cutlery or wipe your face with the napkin. NEVER use it to wipe your nose!
If you excuse yourself from the table, loosely fold the napkin and place it to the left or right of your plate. Do not refold your napkin or wad it up on the table either. Never place your napkin on your chair. At the end of the meal, leave the napkin semi-folded at the left side of the place setting. It should not be crumpled or twisted; nor should it be folded. The napkin must also not be left on the chair.