治疗营养不良性巨幼红细胞性贫血时最好选用：A.硫酸亚铁 B.维生素B12 C.叶酸

某企业于2005年年初向租赁公司融资租入一套价值为200万元的设备，租赁合同规定：租期4年，利率5%，租赁手续费为10万元。分别回答下列问题(计算结果保留两位小数)：

(1)每年年初支付一次租金,计算每期租金并编制租金摊销表;

(2)每年年末支付一次租金,计算每期租金并编制租金摊销表;

(3)每年年初支付一次租金,租赁手续于租赁开始日一次性付清,计算每期租金并编制租金摊销表；

(4)每年年末支付一次租金, 租赁手续于租赁开始日一次性付清,计算每期租金并编制租金摊销表；

(5)以设备的成本为租,每年年初支付一次租金,利息单独计算并按年支付,租赁手金续费于租赁开始日一次性付清,计算每期租金并编制租金及利息摊销表。

(6)以设备的成本为租金，每年年末支付一次租金，利息单独计算并按年支付，租赁手续费于租赁开始日一次性付清，计算每期租金并编制租金及利息摊销表。

可能没有批准文号的药品是（）

A.抗生素

B.中成药

C.中药饮片

D.化学药

频率为（）赫兹范围内的持续振荡现象叫低频振荡。

采用被动管理的管理者(　)。

A．认为证券市场是有效市场，凡是能够影响证券价格的信息均已在当前证券价格中得到反映

B．坚持“买入并长期持有”的投资策

C．认为市场不总是有效的，加工和分析某些信息可以预测市场行情趋势和发现定价过高或过低的证券，进而对买卖证券的时机和种类做出选择，以实现尽可能高的收益

D．经常预测市场行情或寻找定价错误证券，并借此频繁调整证券组合

In a science-fiction movie called "Species", a mysterious signal from outer space turns out to describe the genome of an unknown organism. When the inevitable mad scientist synthesizes the DNA described by the instructions, the creature he breeds from it turns out to resemble Natasha Henstridge, an athletic actress. Unfortunately, the alien harbors within her delicate form the destructive powers of a Panzer division, and it all ends badly for the rash geneticist and his laboratory.

Glen Evans, chief executive of Egea Biosciences in San Diego, California, acknowledges regretfully that despite seeking his expert opinion--in return for which he was presented with the poster of the striking Mr Henstridge that hangs on his office wall--the producers of "Species" did not hew very closely to his suggestions about the feasibility of their script ideas. Still, they had come to the right man. Dr Evans believes that his firm will soon be able to create, if not an alien succubus, at least a tiny biological machine made of artificial proteins that could mimic the behavior of a living cell.

Making such proteins will require the ability to synthesize long stretches of DNA. Existing technology for synthesizing DNA can manage to make genes that encode a few dozen amino acids, but this is too short to produce any interesting proteins. Egea’s technology, by contrast, would allow biologists to manufacture genes wholesale. The firm’s scientists can make genes long enough to encode 6,000 amino acids. They aim to synthesize a gene for 30,000 amino acids within two years.

Using a library of the roughly 1,500 possible "motifs" or folds that a protein can adopt, Egea’s scientists employ computers to design new proteins that are likely to have desirable shapes and properties. To synthesize the DNA that encodes these proteins, Egea uses a machine it has dubbed the "genewriter". Dr Evans likens this device to a word-processor for DNA, on which you can type in the sequence of letters defining a piece of DNA and get that molecule out.

As Egea extends the length of DNA it can synthesize, Dr Evans envisages encoding not just proteins, but entire biochemical pathways, which are teams of proteins that conduct metabolic processes. A collection of such molecules could conceivably function as a miniature machine that would operate in the body and attack disease, just as the body’s own defensive cells do. Perhaps Dr Evans and his colleagues ought to get in touch with their friends in Hollywood.

This passage is mainly（）

A. about a new application of computers

B. a review of a science-fiction movie

C. about synthesizing interesting DNA

D. a survey of scientific breakthroughs