如图所示，弹簧测力计的示数是________N。

无洞口墙梁和开洞口墙梁在顶部荷载作用下，可采用( )进行分析。

A．两种墙梁均采用梁—拱组合模型

B．无洞墙梁采用梁—拱组合模型，开洞口墙梁采用偏心拉杆拱模型

C．无洞墙梁采用偏心拉杆拱模型，开洞口墙梁采用梁—拱组合模型

D．无洞墙梁采用梁—柱组合模型，开洞口墙梁采用偏心压杆拱模型

建设项目法人或建设项目业主对建设项目的管理活动，存在于建设项目全寿命周期，内容包括行政管理和( )两部分。

A．人事管理

B．财务管理

C．专业管理

D．审批管理

（）是早期科林斯柱式的代表作。

牛的前胃包括（）

A.瘤胃

B.网胃

C.瓣胃

D.皱胃

For the first time in the history of the world, every human being is now subjected to contact with dangerous chemicals, from the moment of conception until death. In the less than two decades of their use, the synthetic pesticides have been so thoroughly distributed throughout the animate and inanimate world that they occur virtually everywhere. They have been recovered from most of the major river systems and even from streams of groundwater flowing unseen through the earth. Residues of these chemicals linger in soil to which they may have been applied a dozen years before. They have entered and lodged in the bodies of fish, birds, reptiles, and domestic and wild animals so universally that scientists carrying on animal experiments find it almost impossible to locate subjects free from such contamination. They have been found in fish in remote mountain lakes, in earthworms burrowing in soil, in the eggs of birds — and in man himself. For these chemicals arc now stored in the bodies of the vast majority of human beings, regardless of age. They occur in the mother’s milk, and probably in the tissues of the unborn child. All this has come about because of the sudden rise and prodigious growth of an industry for the production of man-made or synthetic chemicals with insecticidal properties. This industry is a child of the Second World War. In the course of developing agents of chemical warfare, some of the chemicals created in the laboratory were found to be lethal to insects. The discovery did not come by chance: insects were widely used to test chemicals as agents of death for man. The result has been a seemingly endless stream of synthetic insecticides. What sets the new synthetic insecticides apart is their enormous biological potency. They have immense power not merely to poison but to enter into the most vital processes of the body and change them in sinister and often deadly ways. Thus, as we shall see, they destroy the very enzymes whose function is to protect the body from harm, they block the oxidation processes from which the body receives its energy, they prevent the normal functioning of various organs, and they may initiate in certain ceils the slow and irreversible change that leads to malignancy.