锰（Mn）和镍（Ni）都是金属，将镍丝插入硫酸锰溶液中，无变化；将镍丝插入硫酸铜溶液中，镍丝上有铜析出。则Mn 、Ni 、Cu的金属活动性由弱到强排列正确的是(    )

   Good morning! Now let me report the discussion work in our group. Wu Jun cleans up rooms  ____  weekends and Jia Mei likes cooking dinner with her mum. Wang Ping sometimes  ____ (wash) clothes for her family. As for me, I usually help my father water the flowers.
   In my opinion, it is necessary  ____  us students to do some housework by doing it, we can help our parents and understand them better. We’ll also learn to take care of  ____ . Besides, we can relax ourselves from hard work and develop our abilities.
That’s all. Thanks for  ____  ( listen)!