单选题 He always included something above the understanding of his hearers in order to prevent them from becoming______and to stimulate their desire to learn more.
A. pessimistic B. complacent C. perplexed D. complicated

【正确答案】 B
【答案解析】[解析] 四个选项的意思分别是：pessimistic厌世的，悲观的。complacent得意的，自满的。perplexed困惑的，混乱的。complicated麻烦的，复杂的。根据句意，应该选择B。