先导式减压阀中先导阀的作用是()。
A、为主阀提供稳定的气压
B、平衡主阀前后端压力
C、调节主阀后端流量
D、均压
参考答案:A
具有舒筋活络、化湿和胃功效的祛风湿药物是()。
A.独活
B.秦艽
C.木瓜
D.威灵仙
E.五加皮
Smile is recognized as a/an _________ language, which can be understood by people all over the world.
A.artificial
B.technological
C.universal
D.analytical