2017年英语四级阅读理解题库：选词填空（17）

　　El Nino is name given to the mysterious and often unpredictable change in the climate of the world. This strange 47 phenomenon 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 strength, the ocean temperatures rise, causing the Peru current flowing in from the east to warm up by as much as 5℃.

　　The warming of the ocean has far-reaching effects. The hot, humid (潮湿的) air over the ocean causes severe 49 tropical thunderstorms. The rainfall is increased across South America. 50 bringing 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 starvation.

　　El Nino usually lasts for about 18 months. The 1982-83 El Nino brought the most 52 destructive weather in modern history. Its effect was worldwide and it left more than 2,000 people dead and caused over eight billion pounds 53 worth of damage. The 1990 El Nino lasted until June 1995. Scientists 54 estimate this to be the longest El Nino for 2,000 years.

　　Nowadays, weather experts are able to forecast when an El Nino will 55 strike, but they are still not 56 completely 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