—Sorry, I _______ from him recently.

—So you've lived here _______ about seven years.

A

B

    Great changes have taken place in our lives in the last century. Here are some examples:

    Firstly, people were not able to travel such a long distance in such a short time in the past. Planes were not very popular at that time because they used to be a very expensive way to travel. Nowadays, we have fast and comfortable cars, and more and more people can travel by plane.

    Secondly, in the past, people had to work much harder because they did not have the tools that we have today. Today, machines do most of the difficult and dangerous work.

    Thirdly, the living conditions in the past were not as good as they are now. There were no bathrooms or running water in many houses, and many people couldn't buy the things like refrigerators, TV sets or washing machines. Now, most families have several of these things. And many families have computers, cars and so on.

    Finally, nowadays, more and more people have the chance to get a good education. In the past, there were fewer schools and quality of education was much poorer. Now people can also study on the Internet at home.

    The development of science and technology in the world is amazing(令人惊异的). Life now is much faster and busier than it used to be. And we are still creating(创造) new things to make our lives better and easier.

C

    A very important world problem is the growth of population on the earth. The population of the world today is more than 6,500,000,000. That is a great number and we know it quite well. ①The important thing is not how large the population of the world is now, but is the rate(速度) of the growth. It is about 1.63% every year after the number of dead people has been taken away.

    To give you some ideas of the birth rate, look at the ②second hand of your watch. Every second, four babies are born in the world. Another baby! Another baby! Another baby! Another baby! ③You can not speak quickly enough to keep up with the rate of the growth of the population. It is growing faster and faster. So it goes on, hour after hour. In one day, people have to find food for about 350,000 mouths more.

    This great growth of population will make a big problem by the year 2050 — there will be as many as 7,500,000,000 people on the earth! So this is one of the biggest problems that you are going to meet in your life.