题目

如图甲是用气敏电阻改装的酒精含量测试仪电路图，测试仪用以测试汽车司机是否酒驾， 为定值电阻， 为气敏电阻。 的阻值随酒精气体浓度的变化曲线如图乙，电源电动势保持不变。若测试对象呼出的气体中酒精气体浓度越大，则（ ） A . 测试仪中电压表的示数越小 B . 测试仪中电流表的示数越小 C . 电路消耗的总功率越大 D . 电压表与电流表示数的比值越小 Look at the foods around you．From grapes and walnuts（核桃）to cucumbers and spinach（菠菜），they make our diets special. But did you know that none of the foods above are native to China? They came to China through the Silk Road hundreds of years ago．Are there any foods that are native toChina？Of course there are. Rice，soy beans，chestnuts(栗子),Chinese cabbage and hawthorns（山植）were all grown in China first.Where are these foods from?FoodHome countryTime to enter ChinaLuffaIndiaTang Dynasty（AD 618﹣907）EggplantIndia and Southeast AsiaHan Dynasty（206BC﹣AD220）CucumberSouth AsiaHan Dynasty（206BC﹣AD202）WatermelonAfricaTang Dynasty（AD 618﹣907）【1】 came to China through the Silk Road．A. Watermelons and riceB. Grapes and walnutsC. Cabbage and hawthorns【2】 came to China at the same time．A. Cucumbers and eggplantsB. Watermelons and eggplantsC. Cucumbers and watermelons【3】From the text，we know that ．A. luffas are from AfricaB. eggplants are from ChinaC. none of the foods above in the chart are native to China