成对电极间距离（）不成对电极到靠近它的一个成对电极间距离的电极系称为电位电极系。A、

原计划实现全球卫星通讯需发射77颗卫星,这与铱(Ir)元素的原子核外电子数恰好相等,因此称为“铱星计划”。

（1）已知铱的一种同位素是，则其核内中子数是

A.77                B.114                  C.191              D.268     

（2）已知自然界中铱有两种质量数分别为191和193的同位素,而铱的平均相对原子质量为192.22,这两种同位素的原子个数比应为

A.39︰61               B.61︰39                C.1︰1              D.39︰11

D

Mr. Frank shot well and once he had come in fourth in a competition.

Then he went to a big city on business. There he joined the local rifle club. The club had a very good team, which used to take part in a lot of important shooting competitions. One of these took place while Frank was with them. But one of the members of the club's team suddenly fell ill just before the match. The captain had heard of Mr. Frank. He therefore invited Mr. Frank to take the sick man's place.

Mr. Frank felt greatly happy to be asked to shoot for such a good team, but he also felt very nervous, because he was afraid of making a fool of himself.

In fact, he was so nervous that he could not keep his hands from trembling while he was shooting, with the result that he did very badly in the competition. When he took his score card to his captain, he said:" After seeing my score, I want to go outside and shoot myself. " The captain looked at the card for a few seconds and then said, "Well, you'd better take two bullets with you if you want to do that. "

53. Mr. Frank once__________-in a competition.

A. joined the fourth team            B. took the fourth place

C. was the fourth to start shooting     D. shot with the other three

54. Why did Mr. Frank feel nervous to be asked to shoot for the team? Because_______.

A. actually he was not good at shooting

B. he thought the captain and the other members would fool him

C. he was afraid of losing face before so many good shooters

D. he would lose a lot of money if he should fail

55. When Frank said, "After seeing my score, I want to go outside and shoot myself", he meant to say that___________

A. he wants to practice shooting all by himself

B. he wanted to find out the reason for his failure

C. he was too shamed of himself to remain inside and face the captain and the other members

D. he wanted to kill himself with the rifle

56. By saying "You had better take two bullets with you if you want to do that", the captain actually meant to say

A. "We haven't got so many bullets for you to practice shooting."

B. "You can't improve your shooting with only one bullet."

C. "I don't believe you can keep your hands from shaking this time."

D. "you are such a bad shooter that one bullet is certainly not enough to end you life with."

57. According to this passage, which of the following is wrong?

A. He fired several shots and they all missed the target.

B. The captain wasn't satisfied with Frank and laughed at him.

C. In the big city Frank was admitted to the local rifle club.

D. Frank could have done better in the competition.

气雾剂的抛射剂（）

A．Freon

B．Azone

C．Carbomer

D．P010xamer

E．Eudragit L

______对禽甲型流感病毒有明显抑制作用。

恩格勒系统