问题 单项选择题

一群在实验室里研究老鼠体内钙的新陈代谢的科学家发现去除老鼠的甲状旁腺可以导致老鼠血液中的钙的水平比正常水平低得多,这个发现使科学家们假设甲状旁腺的功能是调节血液中的钙的水平。当钙的水平降到正常范围之下,它就升高钙的水平。在进一步的实验中,科学家们不但去除了老鼠的甲状旁腺,而且去除了它们的肾上腺,他们出人意料地发现老鼠血液内钙的水平的下降比单是去除甲状旁腺时慢很多。
下面哪一项,如果正确,能与科学家的假设相一致地解释那个出人意料的发现

A.肾上腺的作用是降低血液中的钙的水平。
B.肾上腺与甲状旁腺在调节血液内的钙的水平时的作用是一样的。
C.甲状旁腺的缺乏能促使肾上腺增加血液中的钙水平。
D.如果只是把老鼠的肾上腺,而没有把其他的腺移去,这只老鼠的血液内的钙的水平将会维持不变。
E.甲状旁腺的仅有功能是调节血液中的钙的水平。

答案

参考答案:A

解析:除掉甲状旁腺,钙的水平下降,因此甲状腺是升高钙水平;同时除掉肾上腺,钙水平下降速度慢了,最合理解释,肾上腺功能是降低钙水平。

单项选择题
单项选择题

Vienna was one of the music centers of Europe during the classical period, and Haydn, Mozart, and Beethoven were all active there. As the (1) of the Holy Roman Empire (which included parts of present-day Austria, Germany, Italy, Hungary, Czech and Slovakia), it was a (2) cultural and commercial center (3) a cosmopolitan character. Its population of almost 250,000 (in 1800) made Vienna the fourth largest city in Europe. All three (4) masters were born elsewhere, but they were (5) to Vienna to study and to seek (6) . In Vienna, Haydn and Mozart became close friends and influenced each other’s musical (7) . Beethoven traveled to Vienna at sixteen to play for Mozart; at twenty-two, he returned to study with Haydn.

Aristocrats from all over the Empire spent the winter in Vienna, sometimes bringing their private (8) . Music was an important part of court life, and a good orchestra was a (9) of prestige. Many of the nobility were excellent musicians.

Much music was heard in (10) concerts where aristocrats and wealthy commoners played (11) professional musicians. Mozart and Beethoven often earned money by performing in these intimate concerts. The nobility (12) hired servants who could (13) as musicians. An advertisement in the Vienna Gazette of 1789 (14) : " Wanted, for a house of the gentry, a manservant who knows how to play the violin well. "

In Vienna there was also (15) music, light and popular in (16) . Small street bands of wind and string players played at garden parties or under the windows of people (17) to throw (18) money. Haydn and Mozart wrote many outdoor entertainment (19) , (20) they called divertimentos or serenades. Vienna’s great love of music and its enthusiastic demand for new works made it the chosen city of Haydn, Mozart and Beethoven.

17()

A.surely

B.likely

C.prefer

D.refer