(8分)在探究滑动摩擦力与哪些因素有关的实验中,小明的实验过程如图所示。 (1)该实验的原理是什么? (2)实验操作的关键是什么? (3)图乙和图丙探究的问题是: (4)由甲、乙两图得到的结论是: 根据短文内容,完成下面各题。 Mary is an English girl, but she lives in China. She is six. Her mother says to her, "You are six now, Mary. You are going to school . I think it is very good . It's a nice school . '' "Is it a Chinese school ?" Mary asks . "Yes, it is.'' her mother says. It is September (九月) and the new school year begins. Mary walks to school every day. She likes her lessons and her classmates very much. Her classmates like her, too . Mary can speak a little Chinese . She likes China . She likes Chinese people and Chinese food a lot 1. Mary comes from ______. 2. She lives in ______ now. 3. She goes to a ______school. 4. She ______ to school every day. 5. She can ______ a little Chinese.