除灰电气一次系统主要以（）电源为主，采用（）系统。
参考答案：380/220V；中性点直接接地
用括号内所给单词的适当形式填空。
1. Is there _______ (somewhere) you want to visit?
2. Have you tried _________ (Italy) food.
3. Li Ling can't enjoy _____ (west) food.
4. There are ____ (many) people in China than in America.
5. Mao Amin is one of famous ______ (music) in China.
下图所示在小轴上铣槽，保证尺寸H和L，所必须限制的自由度个数是（）。
A.六个
B.五个
C.四个
D.三个
