将细菌置于有营养的物体上，它会繁殖并形成细菌群（如图）．以下用来检验两种抗生素杀菌效用的对比实验，最适当的分组设计是（  ）

    Since my mother moved to live with us in the city, she has been much heavier than before. As time went by, her health got1. So I had to take her to see a2. My mother was told to lose weight by doing exercise every day. She had no choice but to follow3the doctor said. I told her that I would exercise with her every morning.

    On the first morning, she got up very early4ran with me in our neighborhood. I tried to run slowly so that she could follow me. After5for some minutes, I told her the proper ways of exercise and the importance of eating healthy food. She listened to me carefully. It made me6that she told me everything very patiently when I was a kid. On the second morning, I praised her for keeping running with me.

    But after two weeks, she wanted to7running because she thought the two-week exercise didn't work at all. To encourage her, I taught her how to use the facilities (设施) for exercise in our8. She began to exercise again.

    With my help, it9her one month to develop a good habit of daily exercise. "Thank you, my dear daughter. Exercise brings health and happiness to me. I will10worry about my health." Her words touched my heart deeply. I felt happy to make a big difference to my mother's life.