根据物权法律制度的规定，下列物权变动中，以登记为变动要件的有（）。 A.甲公司将一块

试说明往复泵流量不均匀的危害性.

如图所示，弹簧测力计的示数是             N。

下表是某实验小组同学做“研究滑动摩擦的大小跟哪些因素有关”的实验记录．

实验次数	接触面的材料	压力F/N	滑动摩擦力f/N
1	木块与木板	4	0.8
2	木块与木板	6	1.2
3	木块与毛巾	6	2.5

（1）分析比较序号1与2的实验数据，可得出的结论是______．

（2）分析比较序号______的实验数据，可得出的结论是：压力相同时，接触面越粗糙，滑动摩擦力越大．

（3）上述研究物理问题的方法叫“控制变量法”，同学们在初中物理知识的过程中，还用到的研究问题的方法有______．

The problem is my weight. I’m just 1.57 meters high, but51. ______
my weight is 75 kilos. Many students often make a fun 52. ______
of me. Some boys were unfriendly for me—they call 53. ______
me "meat ball". That makes me to feel unhappy. 54. ______
Although I’m a bit too fat, yet I feel very well. I 55. ______
enjoy my meal. I love eating meat very much. And I like 56. ______
sweet food, though. I often have sugar with tea, milk. In57. ______
the past two months I had put on 5 kilos. So I’m becoming58. ______
more and more worried this problem, but I don’t 59. ______
know to lose weight quickly. Could you help me, dear doctor. 60. ______

根据我国《献血法》规定，为保障临床急救用血需要，对择期手术患者，应提倡采用的用血方式是

A．互助献血
B．现采现输
C．自身储血
D．自愿献血
E．库血为主