▲ 下篇短文共有 5 個空格，為第 21 至 25 題。   A teacher tried to teach his students a valuable lesson about life by   (21)   a jar, somerocks, pebbles, and sand. At first, the teacher asked his students to watch carefully,   (22)   thenhe filled the jar with rocks. Next, several pebbles were rolled into the spaces between the rocks.   (23)   , the teacher poured enough sand into the jar, which filled into all the tiny crevices.The teacher said the jar was similar   (24)   life. The rocks were the most important thingslike family, friends, and health. The pebbles were all of the secondary things like car, house, andjob. The sand stood for everything else in life   (25)   was small possessions like videogames, clothes, and cell phones. People should always deal with “the rocks” first. This life lessonmade the students think how to lead a happy life.
【題組】21.
(A) use
(B) used
(C) using
(D) to use