第32题: [单项选择]A dam is usually built ______. A. to cover the houses and fields B. for people to have the right amount of water at all times C. to help crops grow better D. to form a large lake 参考答案:B 答案解析:从第二段开头可知,为了解决上述问题,可以在河流上修建水坝,使之能旱季储水,雨季蓄洪。也就是说,使人们总是能有适量的水。[C]为干扰项,修建水坝并不止对农作物起有利的作用。