[单项选择]The most serious damage caused by the viruses is that ______.

Our culture has caused most Americans to assume not only that our language is universal, but that the gestures we use are understood by everyone. We do not realize that waving good-bye is the way to summon a person from the Philippines to one’s side, or that in Italy and some Latin-American countries, curling the finger to oneself is a sign of farewell. Those private citizens who sent packages to our troops occupying Germany after World War II and marked them GIFT to escape duty payments did not bother to find out that "Gift" means poison in German. Moreover, we like to think of ourselves as friendly, yet we prefer to be at least 3 feet or an arm’s length away from others，Latins and Middle Easterners like to come closer and touch, which makes Americans uncomfortable.
Our linguistic (语言上的) and cultural blindness and the casualness with which we take notice of the developed tastes, gestures, customs and languages of other countries, are losing us frien
A. stand still
B. jump aside
C. step forward
D. draw back

Most forest fires are caused by human carelessness or ignorance. Forest fire prevention, therefore, is mainly a problem of creating better understanding of the importance of forests, an awareness of the danger of fire in the woods, and a sense of personal responsibility to safeguard the forests from danger. This is not an easy job.
Careless smokers are responsible for thousands of forest fires each year. Many of these are started when cigarette butts(烟蒂 )and matches are thrown from automobiles. Others are caused by hunter, hikers(徒步旅行 ), fishermen, or woods workers who are careless in disposing of their smoking materials. The Forest Service has posted rules in many of the National Forest that prohibit smoking except in certain designated (指定的) areas. Many of the states have laws against throwing lighted materials from automobiles. The prevention of smoker-caused fires, however, depends upon changing the attitudes and behavior of millions of people who smoke in haz
A. holding the fire damages to a minimum
B. people who have changed their attitude and behavior
C. enough rue fighters with good fire-fighting devices
D. carrying out experiments in "seeding" thunder clouds