题目

第二部分 阅读理解（共25小题。第一节每小题2分，第二节每小题1分；满分45分） 第一节  阅读下列短文，从每题所给的四个选项（A、B、C、D）中，选出最佳选项，并在答题卡上将该项涂黑。   A new study in West Africa shows how farm irrigation systems powered by the sun can produce more food and money for villagers. The study in Benin found that solar-powered pumps are effective in supplying water, especially during the long dry season.   Sub-Saharan Africa is the part of the world with the least food security. The United Nation8、某物质可发生如下反应：2X+2H2O=4KOH+O2↑，则物质X应为（　　）A、KOB、K2OC、K2O2D、KO2