练习材料：
L42-3: Modern cavemen
They plungedinto the lake,
and after loading their gear on an inflatable rubber dinghy,
let the current carry them to the other side.
To protect themselves from the icy water,
they had to wear special rubber suits.
At the far end of the lake,
they came to huge piles of rubble which had been washed up by the water.
In this part of the cave,
they could hear an insistent booming sound which they found was caused by a small waterspouts hooting down into a pool from the roof of the cave.
Squeezing through a cleftin the rocks,
the pot-holers arrived at an enormous cavern,
the size of a huge concert hall.
After switching on powerful arc lights, they saw great stalagmites -- some of them over 40 feet high -- rising up like tree-trunks to meet thestalactitessuspended from the roof.
Round about,
piles of lime-stone glistened in all the colours of the rainbow.
In the eerie silence of thecavern,
the only sound that could be heard was made by water which dripped continuously from the high dome above them.
应用配置：L0+L4
知识笔记：plunged/plʌnʤd inflatable/ɪnˈfleɪtəbəl dinghy/dɪŋi insistent/ɪnˈsɪstənt waterspout/waterspout cleft/klɛft stalagmites /stalagm ites stalactites/stalagmites eerie/ɪr icavern/kævərn
练习感悟：这一大段并没有全部记忆清楚，赶在晚间十二点前匆匆录制完毕，后半段有几个音是发错了的，没有再修改。
