【单选题】The school recommends parents ______ their children to swim in rivers or lakes during summer holidays. [ ]
【简答题】Where does the fresh water come from? It comes from rivers, lakes and__________.
【单选题】热力网中球形补偿器的特点是( )。
A.
补偿能力大,空间小,局部阻力小,投资少,安装方便,适合在长距离架空管上安装,但热媒易泄漏
B.
补偿能力大,占地面积小,成本低,流体阻力小,但热媒易泄漏,维护工作量大,产生推力较大
C.
利用管道自身的弯头来进行补偿,是最简单经济的补偿,在设计中首先采用。但一般补偿量较小
D.
加工简单,安装方便,安全可靠,价格低廉,但占空间大,局部阻力大
【简答题】阅读理解。 Africa is home to nearly 700 lakes and rivers. It holds the largest amount of water on earth. Because of the overuse of the lakes, natural climate changes and other factors (因素), these lakes are...
【单选题】The water in the lakes and rivers in Shandong becomes ______ because of the dry weather .
【简答题】A.poles B.mountains C.rivers D.lakes