个选项中,()具有体积小重量轻、拆装容易,操作灵活轻便,结构简单,造价低廉等优点。缺点是怕杂质,关闭严密性较差。
A、球阀
B、蝶阀
C、截止阀
D、止回阀
参考答案:B
根据首字母或汉语提示完成单词
小题1:Now e (电的)bikes have become more and more popular.
小题2:They are c (疯狂的) about dancing and singing.
小题3: My father works in a big foreign c (公司).
小题4: The building was d (毁坏) by the fire.
小题5:She is s (害怕) of the snake.
21世纪可持续发展的指导思想,坚持以( )为核心。
A.科技发展
B.经济发展
C.教育发展
D.生态和谐