Question

I didn’t know  __________.
A how they called these birds       B what they called these birds
C what his decision is             D how to do with the bad milk

Answer 1

B

主句I didn’t know是一般过去时，所以从句应是过去时态的某种形式，而C和D，不是客观真理，要用是一般过去时，所以排除；在___ they called these birds中缺少called的宾语，所以用B。