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问题 多选题

某卫星在靠近行星表面的轨道上运行，若要计算行星的质量，需测量的物理量是（　　）

A．行星的半径

B．卫星的半径

C．卫星运行的周期

D．卫星的质量

答案

根据万有引力提供向心力G

Mm
R2
=mR(
2π
T
)2得，M=
4π2R3
GT2
，知测量出行星的半径和卫星的运行周期，即可求出行星的质量．卫星属于环绕天体，质量被约去．故A、C正确．B、D错误．

故选AC．

单项选择题

Standard English is the variety of English which is usually used in print and which is normally taught in schools and to non-native speakers learning the language. It is also the variety which is normally (1) by educated people and used in news broadcasts and other (2) situations. The difference between standard and nonstandard, it should be noted, has (3) in principle to do with differences between formal and colloquial (4) ; standard English has colloquial as well as formal variants.

(5) , the standard variety of English is based on the London (6) of English that developed after the Norman Conquest resulted in the removal of the Court from Winchester to London. This dialect became the one (7) by the educated, and it was developed and promoted (8) a model, or norm, for wider and wider segments of society. It was also the (9) that was carried overseas, but not one unaffected by such export. Today, (10) English is arranged to the extent that tile grammar and vocabulary of English are (11) the same everywhere in the world where English is used; (12) among local standards is really quite minor, (13) the Singapore, South Africa, and Irish varieties are really very (14) different from one another so far as grammar and vocabulary are (15) .Indeed, Standard English is so powerful that it exerts a tremendous (16) on all local varieties, to the extent that many of long-established dialects of England have (17) much of their vigor and there is considerable pressure on them to be (18) . This latter situation is not unique (19) English: it is also true in other countries where processes of standardization are (20) .But it sometimes creates problems for speakers who try to strike some kind of compromise between local norms and national, even supranational ones.

16（）

A.press

B.pressure

C.power

D.force
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多项选择题

中暑的主要诊断依据为（）

A.有无在高热环境中长时间工作，未补充水分

B.有无引起机体产热增加的原因存在

C.有无散热增加的原因存在

D.有无散热减少的原因存在

E.有无热适应不良的原因存在
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