珠江三角洲地区能吸引大量民工到来的最主要原因是（　　）

阅读下面四篇短文，从各题所给的A、B、C、D四个选项中选出最佳选项。

    If you meet a British person in the street, it is very likely that he or she will apologize whether it is his or her fault (过错) or not.

    It seems that Britain is becoming a nation where everyone is saying sorry. Almost each person says sorry about eight times each day—and one in eight people apologize as many as 20 times a day.

    As you may have seen, the British apologize more often than members of other cultures. A research shows that in many cases, people's love of saying sorry in Britain goes a little further than it does for Americans. For example, about 15 British people would say ”sorry” while only 10 from the US would do this if they sneezed, if they corrected someone's mistake of if someone knocked into them.

    In the old days, “sorry” was used to express regret and sadness for having done something wrong. But now British people use the expression as a way of showing good manners. For example, they might say “sorry” instead of “excuse me”, “pardon”, “what” or “whatever”.

    People in Britain also use sorry when they share the same feeling with others—so they might say “sorry about the rain”.

    However, British people's use of “sorry” may make things very confusing (迷惑不清) and difficult for foreigners who are not familiar with their ways. But actually, people in Britain pay much attention to the feelings of others. This is the very reason why they apologize every day.

则下列结论：

①AC=AD；

②BD $\perp$ AC；

③四边形ACED是菱形．

其中正确的个数是(    )