Perhaps the most known are the electric rays, or torpedoes, of which several kinds live in warm seas. They possess on each side of the head, behind the eyes, a large organ consisting of a number of hexagonal-shaped cells rather like a honeycomb. The cells are filled with a jelly-like substance, and contain a series of flat electric plates. One side, the negative side, of each plate, is supplied with very fine nerves, connected with a main nerve coming from a special part of the brain. Current gets through from the upper, positive side of the organ downward to the negative, lower side. Generally it is necessary to touch the fish in two places, completing the circuit, in order to receive a shock.
The strength of this shock depends on the size of fish, but newly-born ones only about 5 centimeters across can be made to light the bulb of a pocket flashlight for a few moments, while a fully grown torpedo gives a shock capable of knocking a man down, and, if suitable wires are connected, will operate a small electric motor for several minutes.
Another famous example is the electric eel. This fish gives an even more powerful shock. The system is different from that of the torpedo in that the electric plates run longitudinally and are supplied with nerves from the spinal cord. Consequently, the current passes along the fish from head to tail. The electric organs of these fish are really altered muscles and like all muscles are apt to tire, so they are not able to generate electricity for very long. People in some parts of South America who value the electric eel as food, take advantage of this fact by driving horses into the water against which the fish discharge their electricity. The horses are less affected than a man would be, and when the electric eels have exhausted themselves, they can be caught without danger.
The electric catfish of the Nile and of other African fresh waters has a different system again by which current passes over the whole body from the tail to the head. The shock given by this arrangement is not so strong as the other two, but is none the less unpleasant. The electric catfish is a slow, lazy fish, fond of gloomy places and grows to about 1 metre long; it is eaten by the Arabs in some areas.
The power of producing electricity may serve these fish both for defence and attack. If a large enemy attacks, the shock will drive it away; but it appears that the catfish and the electric eel use their current most often against smaller fish, stunning them so that they can easily be overpowered.
Which of the following can produce the strongest shock?
A. The electric eel.
B. The electric catfish.
C. The newly-born electric torpedoes.
D. The fully-grown electric ray.
建设单位与施工单位按照《建设工程施工合同(示范)文本》签订了施工承包合同。该工程包含两个子项工程,估计工程量甲项为4 000m3,乙项为2 000m3,合同单价甲项为220元/m3,乙项为560元/m3,工程预付款额度为合同价的12%,主要材料和构件所占比重为60%。同时,施工合同中规定:(1)设备由建设单位采购,施工单位安装;
(2)建设单位原因导致的施工单位人员窝工,按18元/工日补偿,建设单位原因导致的施工单位设备闲置,按下表中所列标准补偿;
(3)施工过程中发生的设计变更,其价款按建标[2003]206号文件的规定以工料单价法计价程序计价(以直接费为计算基础),间接费费率为10%;利润率为5%,税率为3.41%。
该工程在施工过程中发生以下事件。
事件1:建设单位采购的设备没有按计划时间到场,施工受到影响,施工单位一台大型起重机、两台自卸汽车(载重5t、8t各1台)闲置5天,工人窝工86工日,工期延误5天。
事件2:某分项工程由于建设单位提出工程使用功能的调整,须进行设计变更。设计变更后,经确认直接工程费增加18 000元,措施费增加2 000元。
上述事件发生后,施工单位及时向建设单位造价工程师提出索赔要求。
该工程预付款的起扣点为()万元。
A. 160
B. 165
C. 170
D. 175