北洋时期中国证券市场包括（）。 A.北洋政府实业、金融业的发展及政府公债的大量发行，

若一个数的立方根等于这个数的算术平方根，则这个数是______．

人们对酸碱的认识，已有几百年的历史，经历了一个由浅入深、由低级到高级的认识过程。我们目前中学课本中的酸碱理论是1887年阿仑尼乌斯(Arrhenius)提出了的电离理论。

(1)1905年富兰克林(Franklin)深入研究了水和液氨的相似性，把阿仑尼乌斯以水为溶剂的个别现象，推到任何溶剂，提出了酸碱溶剂理论。溶剂理论认为：凡能离解而产生溶剂正离子的物质为酸，凡能离解而产生溶剂负离子的物质为碱。试写出液氨自身弱电离的方程式：____________________。

(2)1923年丹麦化学家布朗斯物(Brusted)和英国化学家劳莱(Lowry)提出了质子论。凡是能够释放质子 （氢离子）的任何含氢原子的分子或离子都是酸；凡是能与质子（氢离子）结合的分子或离子都是碱。按质子理论：下列粒子在水溶液中既可看作酸又可看作碱的是__________。

A.H₂O B.NH₄⁺ C.OH^- D.HCO₃^- E.CH₃COO^- F.Cl^-

(3)1923年路易斯(Lewis)提出了广义的酸碱概念。凡是能给出电子对而用来形成化学键的物质是碱；凡是 能和电子对结合的物质都是酸。如：酸（电子对接受体）碱（电子对给予体）反应产物

H⁺ + [:OH]^-→ H:OH 试指出下列两个反应中的酸或碱：

H₃BO₃+H₂O=H⁺+B(OH)₄^- 该反应中的碱是____（填“H₃BO₃”或“H₂O”）

NaH+H₂O=NaOH+H₂↑ 该反应中的酸是____（填“NaH”或“H₂O”）

Insurance is the sharing of (1) . Nearly everyone is exposed (2) risk of some sort. The house owner, for example, knows that his (3) can be damaged by fire; the ship owner knows that his vessel may be lost at sea; the breadwinner knows that he may die by (4) and (5) his family in poverty. On the other hand, not every house is damaged by fire or every vessel lost at sea. If these persons each put a (6) stun of money into a pool, there will be enough to (7) the needs of the few who do suffer (8) . In other words the losses of the few are met from the contributions of the (9) . This is the basis of (10) . Those who pay the contributions are known as (11) and those who administer the pool of the contributions as insurer.
The (12) for an insurance naturally depends on how the risk is to happen as suggested (13) past experience. If the companies fix their premiums too (14) , there will be more competition in their branch of insurance and they may lose (15) . On the other hand, if they make the premiums too low, they will not have (16) and may even have to drop out (17) business. So the ordinary forces of supply and (18) keep premiums at a proper (19) to both insurers and those who (20) insurance.

按照个体成员的时空约束，群决策支持系统有哪四种设置？举例说明。

BGAN727位于屏幕的天线指示灯，绿灯闪烁/慢闪（）.

A.天线可以正常使用

B.天线开始工作

C.天线搜索寻星

D.终端故障