试题题干
Translate the following sentence into Chinese.
We don't know if they all have planets, but we have good reason to think that planetary systems are common.
参考答案
试题解析
考点：have good reason to think有充分的理由相信；planetary system行星系统。
句子结构：句子为but连接的并列句。前半句主干为We don't know，if···为宾语从句。后半句中that引导宾语从句。