题干

在高中阶段,我们学过了很多测量电阻值的方法,某兴趣小组为了测量某个电阻Rx的阻值,设计了如图(a)所示的电路.同学们先用多用表粗略测量了该电阻的阻值,多用表的示数如图(b)所示.然后用如图(a)所示的电路较为精确地测量了Rx的阻值.已知电路中学生电源的输出电压可调,电流表量程均选择0.6A(内阻不计),标有长度刻度的均匀电阻丝ab的总长度为30.00cm.

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阅读下面短文, 从短文后各题所给的四个选项(A、B、C、D)中, 选出可以填入空白处的最佳选项。
    One day,it was raining heavily and I didn't have an umbrella,I had just1a bus and had to walk back to my house.I2walking in that direction,when I heard somebody shouting,“Sister,”“Sister.” I looked back and3the stationery(文具)shopkeeper.I went to him and asked what was the4.He said that since it was raining heavily,I could take a5in his shop,have a look at his new6and go home when the rain stopped.For a moment I hesitated(犹豫),but the7of getting to have a look at the pens made me nod.
    To my surprise,I found that the8was larger than I thought.The stationery shopkeeper offered me a chair and took out the pens for me.I9a beautiful parker(派克)pen and had a try.It10so smoothly that I wanted to buy it with all my heart,11as expected,it was very expensive.The shopkeeper said,“I can give you the pen for ninety-five dollars12one hundred.”I looked up and thanked him for the13,but refused politely as it was14quite expensive for me.By that time,the rain had15,and after appreciating his16,I quickly walked back to my house.
    After that day,the shop became my17place to hang out .The shopkeeper used to18me pens always at discount prices and very often also offered me tea.He had much information about all kinds of pens and other writing instruments.19both of us knew nothing about each other,we had a deep friendship based on our common 20.