[单选题]淋水盘式除氧器，设多层筛盘的作用是( )。-我要搜题网

[单选题]对交流接触器而言，若操作频率过高会导致( )。
A.铁心过热
B.线圈过热
C.触头烧毛
D.触头过热

[不定项选择题]根据下面资料，回答题 They may have lived some 1,700 years ago, but the ancient Maya had an incredible knowledge of celestial bodies, which they believed influenced everything. Now a 15-year-old boy has studied astronomical charts devised by these ancient Mexican people, as well as satellite photos, to pinpoint the location of a forgotten Mayan city. William Gadoury, from Quebec has named the "lost city" in the Yucatan jungle K′aak Chi, or Mouth of Fire. Satellite images suggest the lost city could be among the largest built by the ancient civilisation, which thrived between 300 and 700 A D. Wondering why the ancient people built their cities far away from rivers and in inhospitable mountains prompted the teenager to look to the sky for answers. Incredibly, the brightest of the stars matched the largest cities. "I was really surprised and excited when I realised that the most brilliant stars of the constellations matched the largest Maya cities." He told The Journal of Montreal. He is said to be the first to make the connection, which could lead to further finds. It was in the 23rd constellation, containing three stars, that he found two matching cities on the map, suggesting one has not yet been re-discovered. To investigate further, he used satellite images from the Canadian Space Agency and Google Earth to search the dense jungle for any signs of buildings. The photographs revealed linear features that "stuck out," Daniel De Lisle, from the Canadian Space Agency told The Independent. "There are linear features that would suggest there is something underneath that big canopy," he said. Armand La Rocque, from the University of New Brunswick believes one of the images shows network of streets leading to a large square, which may be a pyramid. "A square is not natural, it is mostly artificial and can hardly be attributed to natural phenomena," he said. It′s possible 30 buildings accompany an impressive pyramid at the site. If true, the lost city would be one of the five largest known to archaeologists, built by the Mayans. Linking the position of stars and the location of a lost city and the use of satellite images on a tiny territory to identify the remains buried under dense vegetation, is quite exceptional. Dr. La Rocque thinks William Gadoury′s technique could lead archaeologists to pinpointing the location of more possible lost Mayan metropolises. Which of the following is NOT TRUE about Maya 查看材料
A.The ancient Maya were interested in celestial bodies.
B.All Mayan cities were built far away from rivers.
C.Maya believed celestial bodies influenced everything.
D.The remains of Mayan cities may be buried under dense vegetation.

[单选题]淋水盘式除氧器，设多层筛盘的作用是( )。A.为了掺混各种除氧水的温度B.延长水在塔内的停留时间，增大加热面积和加热强度C.为了变换加热蒸汽的流动方向D.增加流动阻力

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[单选题]淋水盘式除氧器，设多层筛盘的作用是( )。
A.为了掺混各种除氧水的温度
B.延长水在塔内的停留时间，增大加热面积和加热强度
C.为了变换加热蒸汽的流动方向
D.增加流动阻力