阅读下面短文，掌握其大意，然后从21—40题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上将该项涂黑。
How to Be Polite at a Dinner Party?
It’s not polite to arrive at a dinner more than 15 to 20 minutes late. The host or hostess usually waits for all the 21 to arrive before serving the meal. If someone is late，the food may be spoiled(变味)，and 22 may the host or hostess’ spirits．If you have to be 23 ， call and tell them to start 24 you．
It’s even worse to be early! The host or hostess will probably not be 25 ．If you are early，drive or walk around the block a few times，or just sit in your car until the right time．
Though it’s often 26 to arrive at a party on time，on the
