下列计算结果，正确的是（ ） A．a2•a5=a10 B．a2+a5=a7 C．

有关纤溶酶（PL）的描述，不正确的是（）.

A.单链纤溶酶原（PLG）在t-PA、u-PA作用下，形成双链PL

B.活性中心在重链上

C.PL能分解血浆蛋白

D.PL可将单链t-PA转变为双链t-PA

E.PL能够分解补体

Have you ever wondered why birds sing? Maybe you thought that they were just happy．After all, you probably sing or whistle when you are happy．

Some scientists believe that birds do sing some of the time just because they are happy．However, they sing most of the time for a very different reason．Their singing is actually a warning to other birds to stay out of their territory．

Do you know what a "territory" is? A territory is an area that an animal, usually the male, claims as its own ．Only he and his family are welcome there ．No other families of the same species are welcome．Your yard and house are your territory where only your family and friends are welcome．If a stranger should enter your territory and threaten you, you might shout．Probably this would be enough to frighten him away．

If so, you have actually scared the stranger away without having to fight him．A bird does the same thing．But he expects an outsider almost any time, especially at nesting （筑巢） season．So he's screaming （高声尖叫） all the time, whether he can see an outsider or not．This screaming is what we call a bird's song, and it is usually enough to keep an outsider away．

Birds sing loudest in the spring when they are trying to attract a mate and warn others not to enter the territory of theirs．You can see that birds have a language of their own．Most of it has something to do with attracting mates and setting up territories．

小题1:Some scientists believe that most of the time birds' singing is actually

A．an expression of happiness

B．a way of warning

C．an expression of anger

D．a language of their own小题2:What is a bird's "territory"?

A．A place where a bird may shout at the top of its voice．

B．A place where other bird families are not accepted．

C．An area for which birds fight against each other．

D．An area which a bird considers to be its own小题3:Why do birds keep on singing at nesting season?

A．Because their singing helps frighten outsiders away．

B．Because their singing helps get rid of their fears．

C．Because they want to find outsiders around．

D．Because they want to invite more bird friends．小题4:How does the writer explain birds' singing?

A．By comparing birds with human beings．

B．By reporting experimental results．

C．By describing birds'daily life．

D．By telling a bird's story．

以下各段叙述给出了 5 个计算机专业英文术语的英文解释。这些英文专业术语依顺序分别是(1) 、(2) 、(3) 、(4) 和(5) 。

（1）Messages that are sent electronically over a network.

（2）A series of instructions(commands) performed in a sequence specifying actions to accomplish a task.

（3）The character code built into most modern personal computers.

（4） The minimal unit of information, it can have the value 1 or 0.

（5）The brain of a computer, it contains the ALU, the clock, many registers, the bus interface and circuitry that makes these parts work together.

The character code built into most modern personal computers. （）

A．ASCII

B．internet

C．interface

D．Windows

从外单位取得的原始凭证遗失时，一般应取得原签发单位盖有公章的证明，并注明原始凭证的号码、金额、内容等，由经办单位会计机构负责人、会计主管人员和单位负责人批准后，才能代作原始凭证。 ( )

UML的词汇表包含以下3种构造模块， (16) 是对模型中最具有代表性成分的抽象， (17) 把 (16) 结合在一起， (18) 聚集了相关的 (16) 。

（17）处填（）。

A．规则

B．映射

C．群

D．关系