哺乳动物妊娠时间长，每胎产仔少，繁殖速度比较慢。要加快优良种畜的繁殖速度，目前最好采用的方法是     （   ）                            

    Hello, everyone! I am your1 today. First, I'd like to 2 you something about London before we3London is a very big city of England. The people here are friendly. They are always 4 to tell visitors something about the city.

    London is a busy place. People_5hard. They are very 6 all the time (一直). London is also a very beautiful city. It has a lot of parks and gardens (花园). When you are in London, you can7the British Museum. It can tell you a lot of 8stories. You may also visit9 place. It is the River Thames. It's long and wide. There are many boats on the river.

    May you have a good10！We will get to London in two hours. Now let's have a guessing game.