问题
选择题
—Andy works hard．
—So he does．He is often seen _____ heavily before his teammates have even arrived at practice．
A．to be sweated
B．sweated
C．be sweated
D．sweating
答案
答案：D
考查短语 see sb doing 看到某人正在做某事，此句是被看见正在做某事，应是：sb is seen doing 所以选D 。