跳远起跳蹬伸时的“突停”动作不仅能起（）的作用，而且能减小（）的压力，增加起跳腾起的

计算题：某造球机甲、乙、丙三个班的生球量分别为250t.240t.230t，其作业时间分别为7.5h.7.3h.7.2h，求造球的平均台时产量是多少？

多年生水生草本，地下部有根茎平生或直生，叶浮于水面，圆形或卵形，基部心形，花大而美丽，花瓣8～15片，花期7～9月的花是（）。

A.向日葵

B.百合

C.大丽花

D.睡莲

公安工作的基本方针是( )。

A．坚持专门机关与广大群众相结合
B．坚持打击与防范相结合
C．坚持严肃与谨慎相结合
D．坚持惩办与宽大相结合

决策权定位于群体的每个成员自己手中，领导只做任务布置，不监督检查，完全由员工自行管理，这样的建设项目负责人属于( )领导方式。

A．专制型

B．民主型

C．放任型

D．开放型

Man first appeared on the earth about 2 million years ago. Then he was little more than an animal; but early man had a big advantage over the animals. He had in his brain special groups of nerve cells, not present in animals that enabled him to invent a language and use it to communicate with his fellow men. 46) This ability to speak was of great value because it allowed men to share ideas, and to plan together, so that tasks impossible for a single person could be successfully undertaken by intelligent team-work. Speech also enabled ideas to be passed on from generation to generation so that the stock of human knowledge slowly increased.
It was this special ability that put men far ahead of other living creatures in the struggle for existence. 47) He mastered darkness first with dim lights and later with brighter and brighter lamps, until he can now make for himself so dazzling a light with an are lamp that, like the sun, it is too p for his naked eyes.
48) Man found that his own muscles were too weak for the work which he wanted to do; he explored many other forms of power until now he has his hands on the ultimate source of physical energy, the nuclear power. From man’s earliest days the flight of birds has raised his wonder and desire. Why should he not fly as they did Then he began to experiment. At last he learnt how to make the right machines to carry him through the air. Now he can fly faster than sound. Already he has plans for conquering space, and a series of experiments has been completed. 49) It will not be long now before man takes a giant step away from his planet and visits the moon, learning what it is like to have no weight to his body, no upward direction and no downward.
Man, always a wanderer, has to overcome the difficulty of adapting himself to different climates. 50) Fortunately, in spite of having no. thick skin or warm fur to protect him, he is peculiarly p compared with other living creatures, most of whom are unable to live far outside the region that suits them best.