单选题 A good teacher must know how to______his students to work hard at the subject he teaches.
【正确答案】 B
【答案解析】解析：A项mortify“抑制，约束”；B项motivate“激励，激发”；C项multiply“乘，增加”；D项muster“召集”。根据词意辨析可知B正确。