液体培养基的主要用途是（）。 A.分离单个菌落 B.鉴别菌种 C.观察细菌运

二次函数f（x）=ax²+bx+1，（a＞0），设f（x）=x的两个实根为x₁，x₂，

（1）如果b=2且|x₂-x₁|=2，求a的值；

（2）如果x₁＜2＜x₂＜4，设函数f（x）的对称轴为x=x₀，求证：x₀＞-1．

施工项目负责人是指建设工程项目的（）

A.总经理

B.总工程师

C.项目经理

D.董事长

可与亚硝酸作用显红色的药物是（）

A.硝苯地平

B.卡托普利

C.普萘洛尔

D.胺碘酮

E.氯贝丁酯

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet. Heterogeneous network environments consist of computer systems from (66) vendors that run (67) operating systems and communication protocols. An organization that (68) its computer resources is usually (69) the task of integrating its heterogeneous systems. Typically, each deparlment or division has defined its own network needs (70) OS, LAN topology, communication protocols, applications, and other components.

A．in general

B．in any term

C．in set terms

D．in terms of