II. Cloze Test
        A teacher brought a jar to class because he tried to give his students a life lesson by   16     some rocks, pebbles, and sand. He asked the students to watch carefully and began to fill the jar   17     rocks. Then, he put pebbles and sand. Finally, the jar was full. The teacher said that the jar was similar   18     life. The rocks represented the most important things in life,   19     family and health, while pebbles and sand were less important. People should always take care of “the rocks” first. This life lesson made the students think how they can   20     a happy life.
【題組】16.
(A)use
(B)uses
(C)using
(D)used