在我国的四大地理区域中，江苏省大部分地区位于[ ] A．北方地区 B．南方地区

某人得了胃癌，做了胃部分切除术．某生物兴趣小组的同学为了探究胃液在人体消化中的作用，进行了如下实验．请你帮助完成探究活动的相应内容．

实验材料：A：淀粉糊B：蛋清制成的蛋花液C：花生油

实验仪器：试管、烧杯、温度计、酒精灯、三脚架等

实验药品：盐酸、氢氧化钠、蒸馏水、碘酒等

（1）请你完成下面的实验设计，以验证胃液在化学性消化中的作用．

①胃液的采集：将一只对铃声已建立起食物反射的狗，在其胃底部做一个人工胃瘘（胃液可由胃瘘流到体外），利用铃声刺激空腹的狗，引起它产生分泌胃液的条件反射的方法，可获得纯净的胃液．

②实验材料选择和制备：根据胃液中酶的作用，应选择______（填字母代号）．选择该材料的原因是______，并各取2ml，分装在甲、乙两个试管中．

③验证胃液的化学性消化：

在上表中甲试管对应的a加入2ml胃液，乙试管对应的b加入2ml______．甲、乙试管的水浴温度c应是______，保温约20-30分钟．

④实验结果及其分析：甲试管中物质发生变化（消失），乙试管中物质不发生变化（不消失）．此结果说明：在外界条件适宜的情况下，______．

（2）如果要进一步验证胃液的消化作用在于酶，而不是盐酸．可以在上述实验中再加一个试管丙，在试管丙内d和e处应分别加入______、______，使试管丙应和试管甲形成______．

简述外科感染的演变与转归。

接触器银或银合金触点的积垢应用（）清除干净。

A.小刀

B.细锉

C.砂布

D.汽油或四氯化碳溶剂

The level of lead contamination in United States rivers declined between 1975 and 1985. Federal regulations requiring a drop in industrial discharges of lead went into effect in 1975, but the major cause of the decline was a 75 percent drop in the use of leaded gasoline between 1975 and 1985.
Which of the following, if true, best supports the claim that the major cause of the decline in the level of lead contamination in United States rives was the decline in the use of leaded gasoline

A．The level of lead contamination in United States rivers fell sharply in both 1975 and 1983.

B．Most of the decline in industrial discharges of lead occurred before 1976, but the largest decline in the level of river contamination occurred between 1980 and 1985.

C．Levels of lead contamination in rivers fell sharply in 1975-1976 and rose very slightly over the next nine years.

D．Levels of lead contamination rose in those rivers where there was reduced river flow due to drought.

E．(E) Although the use of leaded gasoline declined 75 percent between 1975 and 1985, 80 percent of the decline took place in 1985.

为何在人员上下车地点必须设置分段开关或自动停送电开关？