电离了的离子气从喷嘴流出时受到孔径限制，使弧柱截面变小，孔径对弧柱的压缩作用称为（）
题型：单项选择题
问题：
电离了的离子气从喷嘴流出时受到孔径限制，使弧柱截面变小，孔径对弧柱的压缩作用称为（）。C
A、热收缩
B、磁收缩
C、机械压缩
题型：单项选择题
阅读理解。
Scientists think that a weather pattern (形式) called El Nino (厄尔尼诺现象) caused the Drought
(干旱) in Australia. E1 Nino causes different weather in different parts of the world. It causes a lot of
rain and floods in some places. It causes droughts in other places. Droughts can badly affect people
and the land. E1 Nino lasts about a year.
In normal weather conditions, warm winds from South America blow from east to west across the
Pacific Ocean. The winds early take storms to Australia. These storms bring rain to Australia.
During an E1 Nino weather pattern, the winds change direction. They blow from west to east across
the Pacific Ocean. The storms no longer move across Australia. So Australia gets very little rain during
E1 Nino.
The drought began in January, 1982. E1 Nino often occurs at this time of year. But that year, El Nino
was stronger than usual. There was very little rainfall (降雨量) in eastern Australia. There was also
very little water in the rivers. The drought was at its worst in February, 1983. At that time, the weather
was very hot. The forests and fields were very dry. Cotton growers eouldn't plant their cotton. Sheep
farmers had no grass for their animals to eat. So many of them died.Because the forests were dry. Forest
fires started quickly. Some of the fires burned for a month. Many forests were destroyed. Over 2,000
people lost their houses in the fires and 75 people died.
The Australian drought of 1982-1983 affected thousands of people and animals. The drought cost
the country over $3,000,000,000. It was a reminder (提示) to Australians of how the weather could
change their lives.
1. From the passage we know El Nino is ______.
A. a powerful storm
B. a place in Australia
C. a weather pattern
2. The undedined word "occurs" in the passage means "______" in Chinese.
A. 发生
B. 发展
C. 消失
3. Picture ______ shows how E1 Nino causes a drought in Australia.
4. W1lich of the following is NOT true according to the passage?
A. There was very little rainfall in eastern Australia in 1982.
B. Many forests weI_e destroyed in the Australian drought.
C. Australian government paid over￥3,000,000,000 for this drought.
5. What's the main idea of the passage?
A. A drought happened in South America.
B. E1 Nino caused a great drought in Australia.
C. Australia got much rain during E1 Nino.
