简述青霉素G的抗菌作用特点。

阅读理解。

     It's sometimes reported that strange objects have been seen high up in the sky. These unidentified(未确认的) flying objects - UFOs have made a lot of people interested. Some of the reports about them are difficult to believe.Some have been explained in scientific ways, others have never been explained.

     It is not easy to decide whether a report is true or not. One report of UFOs came from a British plane on its way from New York to London in 1954. The British plane was flying over an island at 19,000 feet when the captain noticed that something was on their left and a little lower than their plane. It's about five miles away.

     "It was not one object but several," the captain said. "We saw one large and six smaller objects. I sent a radio to report about them and I received the answer that the other planes were coming out to meet us. Before the planes arrived, the smaller objects entered the big objects. The big object then became smaller and moved away fast."

1. Some_____ have been explained in scientific ways.

A. people

B. strange objects

C. of the reports about UFOs

D. planes

2. In 1954, a British plane met a UFO when it was flying from_____ to_____.

A. England, America

B. America, England

C. America, France

D. New York, an island

3. The captain_____ and saw something on the left of their plane.

A. looked down

B. looked up

C. looked back

D. looked ahead

4. How many objects did the captain see?

A. Only one.

B. Five

C. Six

D. Seven

5. The big object moved away because_____.

A. it was afraid of the plane

B. it had received a radio report

C. of some unknown reason

D. it had stayed long enough with the plane

My parents always let me have my own _________of living.

A．way

B．method

C．manner

D．fashion

已知两圆的半径分别为3㎝和4㎝，两个圆的圆心距为10㎝，则两圆的位置关系是（  ）

A．内切

B．相交

C．外切

D．外离

某女，35岁，初产妇，因第二产程延长行会阴后一斜切开及产钳术助产。产后检查：宫底脐下2指，血压15．3／10．7kPa（115／80mmHg）。产后1h产妇感心悸、恶心、口渴、出冷汗，检查 * * 流血不多，色暗红，有血凝块；宫底脐上1横指，软；血压10．6／6．7kPa（80／50mmHg）。最可能的原因是（）

A.子宫收缩乏力

B.凝血功能障碍

C.宫颈裂伤

D.子宫破裂

E.产妇疲劳

点a（0°，20°W），b（20°N，20°E），a在b的方向是（）

A.东南

B.西南

C.西北

D.东北