97免费在线观看视频,亚洲综合自拍网,黄色毛片免费观看,热久久综合网,免费看日产一区二区三区狠狠操av,久久久涩涩涩,在线精品免费视频,人人插天天干,久久91精品国产91久久

<i id="9jq3b"></i>

<pre id="9jq3b"><strong id="9jq3b"></strong></pre>

<dd id="9jq3b"></dd>

單項選擇題

Personnel working with refrigeration systems, and subject to the exposure of refrigerants should wear （）.

A.face shield
B.a respirator
C.rubber gloves
D.an all purpose gas mask

你可能感興趣的試題

單項選擇題

To absorb the wear resulting from impeller rotation and abrasives in the liquid, a centrifugal pump is usually fitted with （）.

A.lantern rings
B.bearings
C.easing volutes
D.wearing rings

單項選擇題

If the capacity of a centrifugal pump decreases gradually over a long period of time, you should replace the （）.

A.packing gland
B.mechanical seals
C.lantern rings
D.wearing rings