什么叫发电机右手定则？
参考答案：将右手掌心让磁力线垂直穿过，大姆指指向导线运动方向，则与大姆指垂直的四指所指的方向为感应电势的方向。
Randy Smith called his broker, Pare Durbin, and asked her to borrow 100 shares of Zylex Corp. stock. Randy then sold the stock at the current market price of $45 while anticipating that Durbin would be able to buy the stock back for him at a lower price in the future. What type of order did Smith place（）
A. Short sale.
B. Market order.
C. Margin order.
我会处理信息：
某市市区总人口数达571600，土地面积32500000平方米，国民生产总值达7963000000元，公共绿地面积9760000平方米．
根据以上信息，完成下列填空：
（1）把总人口数改写成用“万”作单位的数是______万人．
（2）生产总值省略“亿”后面的尾数约是______亿元．
