蒲公英种群密度取样调查过程是（  ）　　
①随机选取若干样方　②计数每个样方的个体数目　③确定某一地段中的蒲公英为调查对象　④计算种群密度　⑤求每个样方的种群密度

   The first telephone cards, produced in 1976, were Italian. Five years later the first British card appeared, and now you can buy cards in more than a hundred countries. People usually start collecting cards because they are small and light and you do not need much space for them. It is also a cheap hobby for beginners, although for some people it becomes a serious business. In Paris, for example, there is a market where you can only buy telephone cards, and some cards cost up to ￡4,000.The first Japanese card has a value of about ￡28,000. Most people only see cards with prices like these in their collectors' magazine.