从每题所给的A、B、c、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
例：It's so nice to hear from her again．______, we last met more than thirty years ago．
A．What's more B．That's to say
C．In other words D．Believe it or not
答案是D。
21．As Susan stared at ______ piles of plastic in her recycling bin, ______ strong sense of responsibility made her stick to her recycling work．
A．不填；不填 B．不填; a C．the ; a D．the; the
22．Tom's mother kept telling him that he should work harder, but ______didn't help．
A．he B．which C．it D．one
