请认真阅读下列短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。
A
More than 1.5 billion people around the world live without electricity. Finding better ways to bring light to the poor is the goal of researchers like Professor Irvine. In the late 1990s, he was working in Nepal when his return flight was canceled. A delay gave him time to take a fourteen-day hiking trip in the Himalayas.
One day he looked in the window of a school and noticed how dark it was. This is a common problem for millions of children around the world. Many families use kerosene oil (煤油) lamps. There are many problems with these lamps. They produce only a small amount of light. They are dangerous to breathe. And they are a big fire danger, causing many injuries and deaths each year. Kerosene costs less than other forms of lighting, but it is still costly in poor countries. Professor Irvine says many peo
