作为承建商，应对什么系统安全负责？
参考答案：
物业消防系统
– You have given us a wonderful Chinese dinner, Mrs Wang.
–____________.
A． I’m glad you enjoyed it
B．Oh, I am afraid I didn’t cook very well
C．Come again when you are free
D．It’s not necessary for you to say so
请在图中任一条磁场的磁感线上标明磁感线方向．小磁针静止时的指向如图，请标出小磁针的N极．
