单选题 26. The policeman on duty became ______ of the youth and asked him why he was standing there.

【正确答案】 B

【答案解析】 suspicious表示怀疑的，用于结构be suspicious of中。A项doubtful形容词adj. 难以预测的，未定的；怀疑的，可疑的；C项suspect vt.猜疑(是)，怀疑(是)，觉得(是)；D项hesitate vi.犹豫；踌躇；迟疑不决。