第24题: [单项选择]The policeman was in plain clothes, watching for a______character at the airport all night. A. suspicious B. suspect C. susceptible D. doubtful 参考答案:A 答案解析:[解析] suspicious意为“令人怀疑的,可疑的”,符合句意;suspect是名词或动词;susceptible意为“敏感的,过敏的”;doubtful意为“疑惑的,怀疑的”,与about,of