每来一届学生,我都对他们讲这样一个故事:在非洲的广场上,有一个黑人在贩卖五颜六色的氢气球。这时来了一个小女孩,指着一个黑色的气球问:“黑色的气球也能飞上天空吗?”“能的。”那黑人商贩告诉她,“只要里面装着氢气,气球就能飞上天空!”说完,挑出一个黑色的气球,一松手,那气球便飞上天空,消 Every time I come to a student, I tell them a story: In Africa, a black man is selling colorful balloons. Then a little girl came to a black balloon and asked, “Can a black balloon fly to the sky?” “Yes.” The black trader told her, "As long as there is hydrogen in it, the balloons can fly. Sky!” Then, pick out a black balloon and let it go. Then the balloon will fly to the sky.