从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。
21. After searching the mall for a whole afternoon, the mom finally bought a nice skirt, as a present for her young daughter, at a _____ yesterday.
A. discount B. bargain C. pay D. cost
22. To make members of team perform better, the trainer first of all has to know their _____ and weaknesses.
A. strengths B. benefits C. techniques D. abilities
