使代数式2（x-5）的值为零的x的值是（ ）

根据对话内容，从方框内的选项中选出能填入空白处的最佳选项，选项中有两项为多余选项。
Mrs. Lee: Hello. 68178502.
David:  Hello.____  ?
Mrs. Lee: Sorry.____ . Can I take a message?
David:  Yes. This is David, Bruce’s friend. I want to ask him for some Chinese ancient coins. He told me he had got some recently. ____  . I don’t care if they were made of different metals. I just want to add some more coins in my collection.
Mrs. Lee: OK. I’ll tell him. Would you like him to ring you back later?
David:  Well, I won’t be at home later this day. Would you please ask him to ring me tomorrow morning?
Mrs. Lee: Sure.____ ?
David:   Oh, sorry.____   The new number is 66129853.
Mrs. Lee: OK. I’ll write a message for him.
David:   It’s really nice of you, Madam. Thank you very much. Goodbye!
Mrs. Lee:  Bye!

观察如图，阴影部分表示四种植物的共同特征，这一特征是（　　）

如图为某静电除尘器工作时内部电场线分布的俯视图，带负电的粉尘被吸附时由b点运动到a点，以下说法正确的是（   ）

现要测定一段粗细均匀、电阻约为60Ω的合金丝的电阻率，若已测得其长度，要尽量精确的测量其电阻值R，器材有：

电池组（电动势3.0V，内阻约1Ω）；

电流表（量程0～100mA，内阻约0.5Ω）；

电压表（量程0～3V，内阻约3kΩ）；

滑动变阻器R₁（0～10Ω，允许最大电流2.0A）；

滑动变阻器R₂（0～500Ω，允许最大电流0.5 A）；

电键一个、导线若干。