题目

   An Australian company, Smart Car Technologies, has developed a system that lets drivers know when they're speeding. When the technology becomes commercially available, it could help lead-footed drivers avoid tickets and also save lives. The company that developed the product hopes to convince Australian government agencies to put the technology into use in their automobile fleets. The product, called Speed Alert, links real-time location data and speed obtained with the help of GPS to a database of posted speed limits stored in a driver's PDA or programmable mobile phone. The setup of the7．与硫化合时，每0.5mol金属原子只失去约3.01×1023个电子的是（　　）A．FeB．MgC．NaD．Cu