四川省2015高考英语人教版一轮讲义：选修6 Unit 5（2）
The other two climbed down into the crater to collect some lava for later study，but this being my first experience，I stayed at the top and watched them.
另外两人攀下火山口去收集供日后研究用的岩浆，我是第一次经历这样的事，所以留在山顶上观察他们。
this being my first experience是独立主格结构。其主要的构成方式如下：
(1)独立分词结构：名称或代词主格＋分词
①The guide leading the way，we had no trouble getting out of the forest.向导领着路，我们毫不费劲地走出了森林。
②He walked into the classroom，h
