皮皮学，免费搜题
登录
搜题
【单选题】
改革开放初期我国旅游业发展的道路是( )。A.
先国内、后入境、再出境
B.
先入境、后国内、再出境
C.
先出境、后国内、再入境
D.
先国内、后出境、再入境
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】What is the function of wearing rings found on some centrifugal pumps ________．
A.
Absorb erosion of high velocity discharge stream
B.
Seal pump shaft against entry of air
C.
Isolate the outlet side from the inlet side
D.
Dampen the turbulent discharge flow
【判断题】Dynamic pumps are classified as centrifugal or axial. axial pumps operate on the principle of centrifugal force.
A.
正确
B.
错误
【单选题】Which of the following pumps belongs to centrifugal pump?
A.
Piston pump
B.
Screw pump
C.
Diffuser pump
D.
Water-ring pump
【简答题】桥式可逆斩波电路用于拖动直流电动机时,可使电动机工作于第 象限。
【单选题】Most pump manufacturers recommend that the suction piping dimension for centrifugal pumps be _____.
A.
one size smaller than the pump suction nozzle
B.
the same size as the pump suction nozzle
C.
one size larger than the pump suction nozzle
D.
installed with a short radius elbow at the pump
相关题目：