问题 选择题

下列物质的用途中利用了氧化还原反应原理的是( )

A.用明矾净水

B.用“84消毒液(有效成分为NaClO)”消毒

C.用食盐腌渍食物

D.用小苏打治疗胃酸过多

答案

答案:B

A是利用明矾水解生成的氢氧化铝吸附造成的。B是利用次氯酸钠的氧化性造成的。C是利用盐溶解使食物和食物所处的环境中的钠离子和氯离子浓度升高,几乎没有生物能在这种环境下生存,食物不易变质。D是利用小苏打的碱性,答案选B。

单项选择题

I was a single parent of four small children, working at a low paid job. Money was always tight, but we had a (1) over our heads, food on the table, clothes on our backs, and if not a lot, always (2) . Not knowing we were poor, my kids just thought I was (3) . I’ve always been glad about that.

It was Christmas time, and although there wasn’t (4) for a lot of gifts, we planned to celebrate with a family party. But the big (5) for the kids was the fun of Christmas (6) .

They planned weeks ahead of time, asking (7) what they wanted for Christmas. Fortunately, I had saved MYM120 for (8) to share by all five of us.

The big (9) arrived. I gave each kid a twenty-dollar bill and (10) them to look for gifts of about four dollars each. Then everyone scattered. We had two hours to shop; then we would (11) back at the "Santa’s Workshop"

Driving home, everyone was in high Christmas spirits, (12) my younger daughter, Ginger, who was unusually (13) She had only one small, flat bag with a few candies—fiftycent candies I was so angry, but I didn’t say anything (14) we got home. I called her into my bedroom and closed the door, (15) to be angry again. This is what she told me.

"I was looking (16) thinking of what to buy, and I (17) to read the little cards on the ’Giving Trees’. One was for a little girl, four years old, and all she (18) for Christmas was a doll. So I took the card off the tree and (19) the doll for her. We have so much and she doesn’t have anything. "

I never felt so (20) as I did that day.

20()。

A.out 

B.over 

C.forward 

D.around

单项选择题