名词性从句第二讲：主语从句 Unit 4 说出that/what/whether 所引导的从句在主句中充当的成分 ，及引导词的功能。 What it was to become was uncertain until between 4. 5 and 3.8 billion years ago when the dust settled into a solid globe. (what 引导_ 从句，并在从句中充当 _) The earth became so violent that it was not clear whether the shape would last or not. (whether 引导_ 从句，在从句中不充当成分) What is even more important is that as the earth cooled down, water began to appear on its surface. (what 引导_ 从句，并在从句中充当_) What many scientists believe is that the continu
