题目

   Global Positioning Systems are now a part of everyday driving in many countries. These satellite-based systems provide turn-by-turn directions to help people get to where they want to go. But, they can also cause a lot of problems, send you to the wrong place or leave you completely lost. Many times, the driver is to blame. Sometimes a GPS error is responsible. Most often, says Barry Brown,an expert in human-computer interaction, it is a combination of the two.    We spoke to Mr. Brown by Skype(网络电话). He told us about an incident involving a friend who had flown to an ai是虚数单位，集合中的元素之和为（   ）A．B．0C．2　　D．3