题目

  We often hear people say, 1 have a good memory for things like that. or I can remember names.     But do you know memory is the single most important thing and it has played a very important part? For early men, there were dangers all around them - bad weather. wild animals. The keys to keep on living lay in man's ability to remember these dangers and the ways he had dealt with them in the pest And as man learned how to deal with them, he became civilized Surprisingly, scientists have not yep found a way to open up the brain and observe its function without destroying it. Perhap4．3人完成一项工程需要3星期又3天（一星期按7天计算），照这样计算，4人来完成这项工程需要2星期又4天．