题干

分类是研究物质的常用方法.右图是纯净物、单质、化合物、氧化物之间关系的形象表示,若整个大圈表示纯净物,则下列物质属于Z范围的是(   )

A:红磷

B:干冰

C:氯酸钾

D:食盐水

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答案(点此获取答案解析)

B

同类题3

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    It was a beautiful Sunday morning, and Maggie and I were returning from our walk through the woods. We were only a couple of blocks from home when I spotted a cell phone and a credit card sitting on the road. We took them home. We always find amazing things on the street and she looks upon them as a movable feast-a chicken wing here or a barbecue rib there.

    I found another cell phone a few years back, too, and called a number in its phone book. I explained the situation to the guy who answered. He said it was his sister's and that he'd come to pick it up, which he did.

    And that was that. No verbal thank-you, no written thank-you, no “here's a box of chocolates” thank-you.

    I didn't have time to call anyone on my latest found cell phone. I was pouring myself coffee when it started to vibrate(震动) and dance across the kitchen counter.

    “Who's this?” someone asked when I picked up.

    “Who's this?” I countered(反问.“Sarah?”

    She was surprised at my knowing her name until she realized her name was on the credit card. “Could you send them to me?” she asked.

    She lives in Arlington, which is 2 miles from my house.

    “Hmm, no, ”I replied, adding that I thought she could come to get them, and that if I wasn't at home, they would be in my mailbox.

    A day later, when I was out for a run, someone retrieved(取回) them. There wasn't even a piece of paper put in the mailbox with “Thanks” on it. In this age of e-mail and cell phone, there's really no excuse. Years ago, I found something more precious than a $100 bill on the street: a driver's license. I saw  that its owner lived a couple of blocks from me, so I called him up. He asked whether I could slip the license through his front door.

    “I guess I could, ”I replied.

    And that was that.