在建筑给水系统中一般采用的泵是（）。A．旋涡泵 B．混流泵 C．轴流泵 D．离心泵

属于半开级配沥青混合料的是（）。

A.沥青玛脂碎石

B.改性沥青稳定碎石

C.沥青混凝土

D.排水式沥青磨耗层混合料

Cooperation is the common endeavor of two or more people to perform a task or reach a jointly cherished goal. Like competition and conflict, there are different forms of cooperation, based on group organization and attitudes.
In the first form, known as primary cooperation, group and individual unite. The group contains nearly all of each individual’s life. The rewards of the group’s work are shared with each member. There is an interlocking identity of individual, group, and task performed. Means and goals become one, for cooperation itself is valued.
While primary cooperation is most often characteristic of preliterate societies, secondary cooperation is characteristic of many modern societies. In secondary cooperation, individuals devote only part of their lives to the group. Cooperation itself is not a value. Most members of the group feel loyalty, but the welfare of the group is not the first consideration. Members perform tasks so that they can separately enjoy the fruits of their cooperation in the form of salary, prestige, or power. Business offices and professional athletic teams are examples of secondary cooperation.
In the third type, called tertiary cooperation or accommodation, latent conflict underlies the shared work. The attitudes of the cooperating parties are purely opportunistic; the organization is loose and fragile. Accommodation involves common means to achieve antagonistic goals; it breaks down when the common means cease to aid each party in reaching its goals. This is not, strictly speaking, cooperation at all, and hence the somewhat contradictory term antagonistic cooperation is sometimes used for this relationship.

The underlined word "fragile" in the last paragraph is closest in meaning to ______.

A．inefficient

B．easily broken

C．poorly planned

D．involuntary

两种发生反应的气体不能共用一根排放管。

经审定的( )应是进行技术设计和施工图设计的投资控制目标。

A．初步设计概算
B．可行性研究报告投资估算
C．修正概算
D．费用预算

沥青针入度试验中，三次测定针入度的平均值为50~149时，则三次测定的针入度值最大差值为（）。

A.2mm

B.4mm

C.6mm

D.8mm