Is the world too crowded? Well, that's a hard question to answer. It's all a matter of perspective .In Montana, you might drive for a mile in any direction and not see another human being. In Macao, 60,000 people live in every square mile! What is true is that the world's population doesn't stay the same. It has been increasing at a very fast rate .That's in part because in each generation  these are more people who then have children than in the last generation. Five hundred years ago, the population of the world was about 460 million. In 1900,the world's population was under 2 billion .Right now it is doubling every 40 years. That means, if this rate of growth continues, when you are a parent, there will be twice as many people on earth as there are now. Wow! Now that's a whole lot of people! Soon the world's population will probably reach 7 billion. Some people worry about that! But there is a lot of disagreement about just how many people on earth equals  too many people. But everyone agrees that the more people there are, the more resources  the world needs to feed, house and take care of all of them, and the more need there is to think carefully about how we live and use the earth's resources. From the passage we can learn that the writer   _  .
thinks the world already has too many people thinks the world can feed no more than 7 billion people is not sure when the world's population will reach 7 billion is not sure what the largest population that the world can feed is