问题如下图：
选项：
A. 
B. 
C. 
解释：
statement 2为什么错？ 市场参与者增加流动性增加，spread降低。
老师好statement 2, 是不是错在说是attramany trars,应该是减少the numbers to trars,但是小量trars,可以做大交易，所以在市场上提供了流动性，所以spre会低，这样的理解对吗？谢谢。
Statement 2 Statement 3 A is correct. Onbuilt, electronic systems are inecheaper to operate thfloor-basetrang systems. They require less physicspath trang floors, anin contrast to floor-basetrang systems, they not require exchange officials to recoranreport prices. Furthermore, the wispreuse of electronic trang systems significantly creasetrang costs for buy-si trars. Costs fell exchanges obtainegreater cost efficiencies from using electronic matching systems insteof floor-basemanutrang systems.These technologies also creasecosts anincreaseefficiencies for the alers anarbitrageurs who provi muof the liquity offereexchanges. Competition forcethem to pass along muof the benefits of their new technologies to buy-si trars in the form of narrower sprea quotefor larger sizes. New electronic buy-si orr management systems also creasebuysi trang costs allowing a smaller number of buy-si trars to process more orrs anto process them more efficiently thmanutrars. While electronic trang hha significant effeon equity markets, it hnot hmuof effeon the markets for corporate anmunicipbon. The market structures of corporate anmunicipbonmarkets have hary changesinthe late 19th century. spite the efforts of many creative velopers of electronic bontrang systems, most public investors in these markets still tra largely over the counter with alers 第二个陈述 最后答案说减少trar？但又增加aler？这怎么理解？
老师，请问为什么电子交易会使trars数量降低呢？我理解电子系统效率更高，trar应该更愿意用，那么应该吸引更多trar才对呀？alers由于sprea低才应该数量减少啊？谢谢
老师， 所以trars 一般是指帮助机构进行购买或者卖是吧， 他们不赚差价是吧？ 但是alers 赚的是spre差价？ 但是因为不需要trar下单，所以trar更少， 但是因为下单便捷，更多aler进来买卖？ 感觉一般大家说自己是trar感觉也是赚差价的职业，但是CFA不是这么定义的是么？
