题目

Nowadays, millions of lonely singles are now going online instead, and therefore,  ___33___ World Wide Web is quickly becoming the world’s most popular matchmaker(媒人).      Singles are flocking(涌向) to the Internet ___34___ (main) because their busy lifestyles leave them little time to look ___35___a significant other. ___36___ (use) dating sites(约会网址) is quick and convenient. Many singles say the regular dating scene has just led them from one bad experience to ___37___ and are ready to try something else. Dating sites also make ___38___ easy to avoid someone in 下列各式不能用平方差公式计算的是（　　）A．（a+2b）（a-2b）B．（x+y）（y-x）C．（-xy+1）（-xy-1）D．（t-3）（3-t）