NO.PZ2018062002000033
问题如下：
Suppose there is an order-driven system that can hide orders, here are four sell orders for the same stock, currently in the system's limit order book. In accordance with the usual common order precedence hierarchy, which of the following orders will have trading precedence？
选项：
A. Order I (time of arrival of 10:02:01).
B. Order II (time of arrival of 10:02:08).
C. Order III (time of arrival of 10:03:04).
解释：
Order III (time of arrival of 10:03:04) has precedence in this transaction. According to the priority of the transaction,first to follow the principle of price priority.In accordance with this principle,sell order II, III, and IV get precedence over order I. The second principle is display priority at a given price, orders III and IV have priority of order transaction because order II is a hidden order. The third principle is time priority at the same price and display status,order III takes precedence over order IV in the transaction.
考点：隐藏订单
隐藏订单通常是一些规模较大的订单，只暴露给接收它们的经纪人或交易所，而不显示在公开的报价单中。
隐藏订单成交优先级只有一种顺序：1、第一价格优先 2、第二显示优先（如果价格相同，非隐藏优先）3、第三时间优先
订单簿中给出的是四个卖单，那么根据成交优先级先看价格，卖的越便宜越先成交，所以I先排除，再看订单的是否显示， III和 IV是非隐藏订单，所以排除II。最后再看时间 III比IV报的时间早，所以 III最先成交。
怎么判断是便宜先成交还是贵的先成交？
