央视记者的调查:鱼翅是以鲨鱼鳍制成,动辄要到几百元甚至上千元一份,然而有业内人士说,在国内市场消费的鱼翅当中,大约四成是靠人造鱼翅来支撑的,早已经形成了一条黑色的利益链。这些鱼翅从合成到鱼翅精调制,到烧碱明胶双氧水泡制,含有大量损伤人肾脏消化系统和致癌的物质(如:砷、重金属等多种有毒有害物质),并可与食品中的淀粉形成环氧酚物质致癌,损伤人肾脏消化系统,严重损坏食用者的健康。结合材料,运用所学知识回答以下问题:
下列熄灭蜡烛的方法中,利用“降低温度到着火点以下”的灭火原理的是( )
如图所示,是探究“电流与电阻的关系”实验电路图,电源电 压保持3V不变,滑动变阻器的规格是“10Ω 1A”.实验中,先在a、b两点间接入5Ω的电阻,闭合开关S,移动滑动变阻器的滑片P,使电压表的示数为2V,读出并记录下此时电流表的示数.接着需要更换a、b间的电阻再进行两次实验,为了保证实验的进行,应选择下列的哪两个电阻()
It was Children's Day yesterday, we 1the park. Our teacher was 2us.
3 many people there. Some Young Pioneers (少先队员)4 near the river.
5 sang and danced. There were some6 on the river. There was a hill
7. Some boys8 in the river. We sat under 9 apple tree with our teacher. We 10on Children's Day yesterday.