安排涉外宴请的用餐环境，主要需要注意四点：第一，环境要（）；第二，环境要（）；第三，环境要（）；第四，环境要（）。
参考答案：幽静；雅致；整洁；卫生
根据句意，用首字母适当的形式填空。
1. It's cold now. please put on your s_______.
2. In summer Bill likes to wear s______, and Helen likes to wear skirt, too.
3. How ______ are the pants? It's 30 dollars.
4. You cant' run fast without a pair of s_______.
5. Do you know that old man with a black h_______ over there?
直线a上有四个点，点A，点B，点C，点D，那么直线a上共有________________条线段；
