A.Its a narrow street of medieval houses.B.Its the palace where the Queen lives when

A．It"s a narrow street of medieval houses.

B．It"s the palace where the Queen lives when she comes to Edinburgh.

C．It"s where the Scottish government used to be.

D．It"s where the Scottish kings and queens used to live.

请帮忙给出正确答案和分析，谢谢！