题干

小王用天平和量筒测量矿石的密度,有如下一些实验步骤:

①用调节好的天平测出矿石的质量m;

②向量筒中倒进适量的水,测出这些水的体积V1

③根据密度的公式,求出矿石的密度ρ;

④将矿石浸没在置筒内的水中,测出矿石和水的总体积V2

他应采用的正确的实验步骤顺序为(  )

A:①②③④

B:①②④③

C:②③①④

D:②③④①

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答案(点此获取答案解析)

B

同类题2

阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

    When I was 12, all I wanted was a signet (图章) ring. They were the "in" thing and it seemed every girl except me had one. On my 13th birthday, my Mum gave me a signet ring with my initials(姓名首字母) carved into it. I was in heaven.

What made it even more special was that it was about the only thing that wasn't being "re placed". We'd been burnt out in fires that swept through our area earlier that year and had lost everything—so most of the " new" stuff (东西) we got was really just to replace what we'd lost. But not my ring. My ring was new.

    Then, only one month later, I lost it. I took it off before bed and it was missing in the morning. I was sad and searched everywhere for it. But it seemed to have disappeared. Eventually, I gave up and stopped looking for it. And two years later, we sold the house and moved away.

    Years passed, and a couple of moves later, I was visiting my parents' when Mum told me that she had something for me. It wasn't my birthday, nor was it Easter or Christmas or any other gift-giving occasion. Mum noticed my questioning look. "You'll recognize this one," she said, smiling.

Then she handed me a small ring box. I took it from her and opened it to find my beautiful signet ring inside. The family who had bought our house 13 years earlier had recently decided to do some redecorations, which included replacing the carpets. When they pulled the carpet up in my old bedroom, they found the ring. As it had my initials carved into it, they realized who owned the ring. They'd had it professionally cleaned up by a jeweler before sending it to my mother. And it still fits me.