【简答题】Every possible means ______ to pr the air pollution, but the sky is still not clear. A) is used B) are used C) has been used D) have been used
【单选题】在行星齿轮机构中,单排行星齿轮机构总共能提供 ( )种不同的传动比。
【单选题】在单排单行星轮式行星齿轮机构中,总共能提供 种不同的传动比。
【单选题】防淹门系统作为轨道交通( )线路的防灾设备,是在区间隧道突发事故时,阻止江河水涌入地铁车站的有效屏障,它能有效保护地下设备和保障人员安全。
【单选题】You can, the sky is clear, see as far as the old temple on top of the mountain, but not today.