Question

I don't know ________！

1. A.
   where the post office was
2. B.
   where the post office is
3. C.
   where's the post office
4. D.
   where was the post office

Answer 1

B
本句的意思是“我不知道邮局在哪儿”。Where引导了一个宾语从句。宾语从句要用陈述句语序，Where the post office is作know的宾语。