①HCl比H2S稳定;②HClO4酸性比H2SO4强;③Cl2能与H2S反应生成S;④Cl原子最外层有7个电子,S原子最外层有6个电子;⑤Cl2与Fe反应生成FeCl3,S与Fe反应生成FeS;⑥盐酸是强酸,而氢硫酸是弱酸.
A:①②③④⑤⑥
B:①②③④⑥
C:①②③⑤
D:②④⑥
已知(a+b)2=16,ab=4,求a2+b2与(a-b)2的值.
根据2013年市环保局监测站对X河水质检测结果绘制的简图如图2所示。请据图示回答下列问题:
A:Hi, Li Ming.
B:Hi, Mrs Li.
A:What are you doing?
B:I'm reading a story book. What are you doing?
A:I'm writing a letter. May I look at your story book?
B:Certainly. Here you are.
A:Thank you.
56÷14=____
640÷40=____
2700÷3=____
620÷31=____
蚕丝是高级的纺织原料,被称为“纤维皇后”“第二肌肤”的美称。( )