问题 多项选择题

软管卷盘水压试验台应符合下列要求:()

A.水压源的额定工作压力应不低于相应软管卷盘额定工作压力的3倍

B.压源的额定工作压力应不低于相应软管卷盘额定工作压力的2倍

C.当系统内水压不大于3.0MPa时,压力显示器所显示的压力波动值应大于±0.03MPa,水压大于3.0MPa时,压力波动值应不大于±0.05MPa

D.压力显示器的下限为0,上限为试验所需压力值的1.5~3.0倍范围内,精度不低于±1.5%

答案

参考答案:A, B, C

单项选择题

American Museum of Natural History is one of the largest natural and historic museums in the world and one of the main natural history research and education centres in the United States, set up in 1869 and located in the west of the Central Park, Manhattan District, New York. It (1) 7 hectares in its total area, (2) classical types of buildings. The (3) of ancient creatures and humanity is (4) the first place of all the museums in the world, (5) the representative samples from South America, Africa, Europe, Asia and Australia were collected, besides those from the (6) country, the United States.

In the museum, there are five kinds of exhibits, including astronomy, mineralogy, human history, and animals in the (7) times and those in modern times. There are thirty-eight exhibition halls with different (8) from 500 to 1,500 square metres. Besides these, there is a Roosevelt Memorial Hall in (9) of President Roosevelt who supported the (10) of the museum, which is also used to have a special exhibition, showing the new important (11) on natural sciences and (12) affairs and social problems, and special topics connected closely with the life of the citizens. Besides this, it is also used for avocation (13) to have all kinds of scientific activities in the laboratories, centres of natural science and centres for citizens. There are more than 10 (14) research departments mainly (15) for collection of samples, research and work of publication.

In the museum, there are (16) and sub-libraries of Aulspond ancient amniote, with about 300 thousand books and magazines (17) natural history, many of (18) are very valuable monographs for the first edition. It has published many expert books and magazines, and a large number of propaganda materials, (19) which are the two magazines, Natural History and Members of Museum that have the biggest (20) of their magazines.

2()

A.with

B.of

C.in

D.on

单项选择题