Shouldn't it be translated as "please, sit down"?
They probably can translate it as "please have / take a seat".
Your answer, or "please take a seat." would also be acceptable in English
These look a bit alike:
请 (qǐng) = please
谁 (shéi) = who
請坐下來 （Please sit down) should also be accepted. I was marked wrong.
Me begging my dog to learn a trick