Doing exercise can ____ us healthy.
A.makes B.TO make C.making D.make
答案：D
解析：∵动词作主语时,须用它的动名词形式,即在动词原形后＋ing,
∴开头为Doing exercise.
∵can是情态动词,而情态动词后必须＋动词的原型,
∴中间部分为can make us.
整句连起来就是Doing exercise can make us healthy.
意思：做运动可以使我们健康.