有3户人家共订了10份日报，每户人家至少2份，最多4份。问：一共_爱下问搜题

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问题单项选择题

有3户人家共订了10份日报，每户人家至少2份，最多4份。问：一共有多少种不同的订法( )

A．6
B．12
C．18
D．21

答案

参考答案：A

解析：设有甲、乙、丙三户人家，依题意，当甲订2份时，乙、丙必须各订4份，此种情况就此1种；当甲订3份时，则乙、丙可分别订3或4份，有2种情况；当甲订4份时，则乙、丙可都订3份，或者分别订2份或4份，共有3种情况，则共有1+2+3=6种。故选A。

选择题

如图所示为一种早期的自行车，这种不带链条传动的自行车前轮的直径很大。若某人骑着自行车向前行驶时，关于该自行车的前、后轮轮缘各点，下列说法正确的是

A．线速度大小相同

B．角速度相同

C．向心加速度大小相同

D．在相同时间内通过的路程相同

完形填空

You heard about the sign posted on a farmer's fence? On the other side of the     resides the biggest, meanest looking    you can imagine．The sign is intended to strike    into the hearts of would-be trespassers．It reads, "Don't attempt to    this field unless you can do it in 9．9 seconds．The bull can do it in 10 flat!"
Don't try to cross that field unless you are        !And isn't that the way it is in life? We have to be ready when the     arises or else we will have little chance of    ．
Sixth-grade schoolteacher Ms Shelton believed in    ．Students remember how she    in on the first day of class and began writing    of an eighth-grade caliber on the chalkboard．They    protested that the words were not on their    and they couldn't learn them．
Their teacher        that the students could and would learn these words．She said that she would       teach down to them．Ms Shelton ended by saying that one of the students in that classroom could go on to      ．maybe even be president some day, and she wanted to prepare them for that day．
Ms Shelton spoke those words many years ago．    did she know that someday one of her students - Jesse Jackson - would take them     ．She believed that if they were well prepared, they could achieve     goals．
Ralph Waldo Emerson once said, "People only see what they are prepared to see．"     that's true, then it is also true that they only become what they are prepared to become． And a lot of         is just about getting ready．

A．accompanied

A．opportunity

A．determination

D．requirement