题目

阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上将该项涂黑。Tu Youyou, 84, honored with the Nobel Prize in Physiology or Medicine on Oct 5, 2015. She was the first Chinese citizen to win a Nobel Prize in science for her work in helping to create an anti-malaria(疟疾) medicine. In 1967, Communist leader Mao Zedong decided there was an urgent national need to find a cure for malaria. At the time, malaria spread by mosquitoes was killing Chinese soldiers fighting Americans in the jungles of northern Vietnam. A secret resea方程和（,），所表示的曲线可能是（ ）