哪块陨石被称为地球年龄研究史上的“罗塞塔碑”（） A.阿林陨石 B.威拉姆特陨石 C

氦原子被电离出一个核外电子，形成类氢结构的氦离子．已知基态的氦离子能量为=－54.4eV，氦离子能级的示意图如图所示．在具有下列能量的粒子中，能被基态氦离子吸收而发生跃迁的是（填正确答案标号．选对1个得3分，选对2个得4分，选对3个得6分．每选错1个扣3分，最低得分为0分）

A．54.4eV（光子）

B．50.4eV（光子）

C．48.4eV（电子）

D．42.8eV（光子）E．41.8eV（电子）

在文件系统阶段，操作系统管理数据的基本单位是( )。

A．文件

B．记录

C．程序

D．数据项

非特异性淋巴结炎的主要特点是()。

A．直径超过1cm

B．质地较硬

C．压痛明显

D．与周围组织粘连

E．多成串存在

It is clear that some chemicals can damage the health of animals and humans. (1) , this is not the only problem that (2) be caused by the careless use of chemicals. Chemicals can also (3) the ecological balance of the environment. If the ecological balance is disturbed, the results can be (4) serious.

The (5) of DDT illustrates the problem. DDT, a chemical which kills insects, at first seemed to be a perfect answer (6) many problems. It would control insects that caused dangerous diseases, (7) insects that caused billions of dollars of damage to crops every year. Governments permitted and even (8) the use of DDT. Farmers in many countries (9) to spray it on their crops. The (10) results were good: Damage to crops (11) down, and profits went up. However, the chemical had effects which the scientists didn’t see in (12) . First, it also killed insects which were the (13) enemies of the harmful insects and which were therefore beneficial to farmers. Second, and perhaps worse, DDT did not kill (14) harmful insect. A few insects had natural resistance to the chemical. They (15) and reproduced in large numbers. In a few years there were large numbers of insects which were not (16) by DDT, and there were (17) insects which could act as natural (18) on these new "super-insects". Finally, it became clear that DDT was not solving the insect problem. In fact, it was making the problem worse. It (19) became necessary to find a second (20) for the effects of the first.

1（）

A.Therefore 

B.However 

C.Meanwhile 

D.Besides

目前华为交换机中支持整机休眠技术的交换机是（）。

A、5700-LI

B、5700-SI

C、5700-EI

D、5700-HI