循环波动

Groundbreaking research by two french geophysicists promises to shed some light on the mystery.using 80 metres of deep sea sediment core, they have obtained measurements lots of magneticfield intensity that span 11 polarity reversals and four million years.the analysis reveals that intensity appears to fluctuate with a clear, welldefined rhythm.although the strength of the magnetic field varies irregularly during the short term, there seems to be an inevitable longterm decline preceding each polarity reversal.when the poles flip―a process that takes several hundred thousand years―the magnetic field rapidly regains its strength and the cycle is repeated.

答案为d。这一题目是根据上下文判断词意的题。flip的意思是&快速翻转&，它所在的句子的意思是&当两极互换――这一过程需要上万年的时间――磁场会很快重新恢复它的强度，新的一轮循环又开始了。&因此在四个选项中： a.decline的意思是&拒绝；变小、变弱&，b.intensify的意思是&变得更强烈、加剧&，c.fluctuate的意思是&涨落、波动&；d.reverse的意思是&使反转、倒退、颠倒&，例如：writing is reversed in a mirror。写出来的字在镜子里是颠倒的。d的意思与flip最接近。

Chrysanthemum of 10 thousand birthday is lax to edaphic requirement, with the arenaceous qualitative loam with fecund, good drainage had better.

万寿菊对土壤要求不严，以肥沃。排水良好的砂质壤土为好。

He unstepped the mast and furled the sail and tied it.

他拔下桅杆，把帆卷起，系住。