They haven't decided where they should build a new train station.复合句变简单句.
问题描述：
They haven't decided where they should build a new train station.复合句变简单句.
They haven't decided ___ ___ ___ a new train station.
答
They haven't decided where to built a new train station.
用疑问词加不定式就可以了
你发的原句才是宾语从句,引导词是where,where to do不是句子,它可以直接做decide的宾语且又变成了一个简单句