跨度大于（）m的梁不得采用搭接接头。

完形填空II. 根据所学语段，用适当的词填空。请同学们务必看清题目要求，限做指定题目。(共8个小题；每小题1分，满分8分)

(长郡生试题)   Another drug that has helped increase the standard of people’s   41  is penicillin. This bacteria-killing medicine is considered by many to be one of the most   42   medicines in contemporary society. It was discovered by   43  Scottish scientist named Alexander Fleming in 1928. He noted that mould had grown on a special transparent jelly that had bacteria on it. Fleming tried this mould   44  on another bacterium and found that it killed the bacteriun   45  . He named the chemical found in the mould ‘penicillin’ and tried to make it pure to be a medicine.

46    , it was not until World War Ⅱ   47  two other scientists managed to use new chemical techniques to purify it. They were able to produce it in large    48   .

如图所示，水平方向的匀强电场和匀强磁场互相垂直，竖直的绝缘杆上套有一带负电的小环。小环由静止开始下落的过程中，所受的摩擦力：

A．始终不变

B．先增大后不变。

C．先减小最后为零

D．先减小后增大，最后不变。

关于劳动争议解决，说法错误的是

A．劳动者请求社会保险经办机构发放社会保险金的纠纷不属于劳动争议；

B．个体工匠与帮工、学徒之间的纠纷不属于劳动争议

C．农村承包经营户与受雇人之间的纠纷不属于劳动争议

D．用人单位拒付工资引起的纠纷不属于劳动争议

联合国是当今世界最重要的国际组织，下列关于安理会的表述正确的是（）

①对维护国际和平与安全负主要责任

②对实质性问题的审议坚持“大国一致”原则

③对实质性问题的审议，五个常任理事国必须都投赞成票

④是和平解决国际争端的司法机构

A、①②③

B、②③

C、①②

D、①②③④

设备更新选型应遵循什么原则？其相互间关系如何理解？