练习材料：

L42-2: Modern cavemen

The deepest known cave in the world is the Gouffre Berger near Grenoble. It extends to a depth of 3,723 feet. This immense chasm has been formed by an underground stream which has tunneled a course through a flaw in the rocks. The entrance to the cave is on a plateau in the Dauphine Alps. As it is only six feet across, it is barely noticeable. The cave might never have been discovered had not the entrance been spotted by the distinguished French pot-holer, Berger. Since its discovery, it has become a sort of pot-holers' Everest. Though a number of descents have been made, much of it still remains to be explored. A team of pot-holers recently went down the Gouffre Berger. After entering the narrow gap on the plateau, they climbed down the steep sides of the cave until they came to a narrow corridor. They had to edge their way along this, sometimes wading across shallow streams, or swimming across deep pools. Suddenly they came to a waterfall which dropped into an underground lake at the bottom of the cave.

任务配置：L0+L4

知识笔记：

immense /ɪ'mɛns/adj.巨大的extremely large＝enormous

chasm /'kæzəm/ n.裂隙，深坑a very deep space between two areas of rock,ice,especially one that is dangerous.

tunnel v.挖掘(隧道)

flaw n.缺点

plateau /plæ'to/ n.高原

noticeable adj.显而易见的

corridor n.走廊

edge v.(使)徐徐移动

wade v.涉水

across adv.宽

as表原因，引导原因状语从句as it is only six feet across,......

if省略，从句部分倒装

Everest n.珠穆朗玛峰

练习感悟：

Never leave the things until tomorrow you can do today.