根据语境。填人适当的词语或句子补全对话。

A: Where are you from?

B: I'm from Korea.

A: What are 1.            manners in your country?

B:  Korea is a country famous for its many native dishes.  2.           food is rich in nutrition, well-balanced

and low in calories.  They say that you can eat as much Korean food as you like and never gain weight.

A:  Wonderful.  I eat 3.           .  I like to eat nice things and keep slim at the same time,

B: Come to Korea then.

A: Is Korean food chiefly made of 4.           ?

B: Yes, it is. Seasonings include garlic, red peppers, scallions, soy saucey fermented bean paste, ginger

and sesame oil.

A: 5.           . the old or the young?

B: Of course, the oldest eat first.  They are respected most in our country.

蒸发量为1t/h的锅炉，其省煤器上装有两个安全阀，为确保锅炉安全运行，此锅炉至少应安装的安全阀数量为（）。

A．3个

B．4个

C．5个

D．6个