单选题 The student union's president was appalled by the {{U}}complacency{{/U}} of his classmates; not one of the seniors seemed to care about the theme of the band.
【正确答案】 D
【答案解析】[分析] 形近词辨析 A．compliment称赞，恭维，致意；B．complement补足物，补语；C．commitment许诺，承担义务，委托事项；D．contentment满意，知己；而complacency表示：安心，满足；因此答案为D。