听力原文： A key point in the discussion of illegal immigration (and legal immigration, for that matter) is that many of those who are vehemently opposed to illegal immigration are also opposed to large amounts of legal immigration as well. These thinly hidden agendas mean that often the debate on illegal immigration cannot be separated from the debate on legal immigration. Americans firmly believe' in tough laws against illegal immigrants and 70% of Americans want no more than 300,000 legal immigrants to enter the U. S. per year. In fact, 20% of Americans want immigration completely stopped. Taking these numbers as the truth, it is clear that America thinks that we have too many immigrants. Such a dislike of immigration is interesting considering the success of past immigration. Many people would say that today's immigrants are somehow different than those of the past. However, the truth is that the similarities between the immigrants of today and those of the past are numerous. Their reasons for coming to this country are often similar. When illegal immigration is not confused with legal immigration, debate can take place in a sane manner. Outlandish solutions like building a huge 2,000 mile-long fence and gathering a virtual army to defend the border from Mexicans are not the answer. Making legal immigration easier and more common is the best solution that we have now. What is the most difficult part in the issue of illegal immigration, according to the passage you have just heard?