韵头
参考答案：
介于声母和韵腹之间，表示复韵母的发音起点，发音轻而短。
The Network Coordination station for the INMARSAT-A coast stations in the Pacific ocean region is in（）.
A.Yamaguchi, Japan
B.Beijing, China
C.Nakhodka, Russia
D.Perth, Australia
S-70标号石油沥青胶适用的屋面坡度是：（）.
A.3%～15%
B.15%～25%
C.25%～30%
D.＞30%
