( )是搞好导游服务工作的前提。
A．丰富的知识
B．熟练的技能
C．娴熟的语言
D．良好的身体
参考答案：A
He's succeeded in many scientific fields. However, his wife is an ordinary woman, _____?[ ]
A. is she
B. isn't she
C. doesn't he
D. hasn't he
压力容器的安全阀定期校验周期为（）。
A、六个月
B、一年
C、二年
D、不定期限
