Galapagos Islands show that some 4,000 years ago, an El Nino occurred only 60 years or so. Studies of tree rings and ice cores indicate a more recent cycle of seven years, still much less frequent than the present cycle of every three or four years.

　　The other alternative? Records are accurate enough to show that we’re in the second El Nino�瞚ntensive era of the past 100 years. The first was during the 1920s and 30s, and probably was responsible for the Dust Bowl, when drought destroyed hundreds of farms in Oklahoma and north Texas. The second seems to have started around 1976. These shifts seem to be periods of natural warming in the Pacific. The warming does not necessarily cause El Nino but certainly amplifies it, creating the appearance of more and more severe El Nino. (380 words)

　　1. The picture as depicted by the writer in the first paragraph seems to be .

　　[A] fairly reassuring.

　　[B] very bleak.

　　[C] rather shocking.

　　[D] quite exceptional.

　　2. The idea of the “global�瞱arming�瞐s�睧l Nino�瞚nstigator” roughly refers to be .

　　[A] contribution of global warming to the occurrence of El Nino.

　　[B] unusual behavior of El Nino in the past two decades caused by global warming.

　　[C] caution shown by authorities against the destruction of El Nino.

　　[D] accurate forecast for the approach of El Nino.

　　3. The possible explanations of El Nino is the following EXCEPT .

　　[A] global wa