资料题：When we make friends, we consider such hings as age, race, and background, because（　）。

There are some steps you can take yourself to avoid catching a cold.Contrary to popular belief, colds are not caused by exposure to severe weather.Colds are caused by viruses harbored in the body, and you're better of out on the ski slopes or even waiting for the bus on a snowy day than you are in a toasty warm room surrounded by friends, co-workers, or fellow students, who just may be passing the virus around.If you feel a chill when you' re coming down with a cold,you' re already sick.A chill is an early symptom: it's the cold that causes the chill, not the other way around.While the virus can spread through droplets propelled into the air when a cold - sufferer coughs or sneezes, surprisingly, this is not the most common route of transmission.Numerous studies have now shown that the overwhelming majority of colds are"caught" by hand contact."A cold-sufferer rubs her nose, thereby transferring"the virus to her hand.Then a friend comes to visit."Don't kiss me,”she cautions, so the fiend steps back and presses her hand.The friend then wipes her own nose or eye-and several days later is stricken with a cold.Or parents pick up their child's abandoned tissues and carefully throw them away, but fail to wash their hands afterwards.Cold viruses also can be transferred to objects-telephones, towels, plates-and remain infectious for up to three hours.Frequent hand-washing- on the part of the cold-sufferer as well as other members of the household-will minimize the spread of viruses in this way.