El Nino is the name given to the mysterious and often unpredictable change in the climate of the world. This strange 47 happens every five to eight years.
It starts in the Pacific Ocean and is thought to be caused by a failure in the trade winds(信风), which affects the ocean currents driven by these winds. As the trade winds lessen in 48 , the ocean temperatures rise, causing the Peru current flowing in from the east to warm up by as much as 5 °C.
The warming of the ocean has far-reaching effects. The hot, humid (潮湿的) air over the ocean causes severe 49 thunderstorms. The rainfall is increased across South America, 50 floods to Peru. In the West Pacific, there are droughts affecting Australia and Indonesia. So while some parts of the world prepare for heavy rains and floods, other parts face drought, poor crops and 51.
El Nino usually lasts for about 18 months. The 1981-83 El Nino brought the most 52 weather in modern history. Its effect was worldwide and it left more than 2,000 people dead and caused over eight billion pounds 53 of damage. The 1990 El Nino lasted until June 1995. Scientists 54 this to be the longest El Nino for 2,000 years.
Nowadays, weather experts are able to forecast when an El Nino will 55 , but they are still not 56 sure what leads to it or what affects how strong it will be.
A) estimate
B) strength
C) deliberately
D) notify
E) tropical
F) phenomenon
G) stable
H) attraction
I) completely
J) destructive
K) starvation
L) bringing
M) exhaustion
N) worth
O) strike
参考答案：
47. P phenomenon
48. B strength
49. E tropical
50. L bringing
51. K starvation
52. J destructive
53. N worth
54. A estimate
55. O strike
56. I completely
