估一估，大约有____只羊．说说你是怎样估计的？
—I want to see Mr. White. We have an appointment.
—I'm sorry, but he is not ________ at the moment, for the meeting hasn't ended.
如图所示,根据平面镜成像的特点在图中画出平面镜.
下列四组省区全部属于东部经济地带的是( )
