试题题干
Translate the following sentence into Chinese.
We know pretty well how stars are born because we can observe them. Two or three new stars appear in our galaxy every year.
参考答案
试题解析
考点：we know pretty well 我们确切知道······；galaxy 星系。
句子结构：第一句为主干为We know pretty well，how stars are born为宾语，because引导原因状语从句。第二句为一个简单句。