下列两个变量x、y不是反比例的关系是（ ）
A．书的单价为12元，售价y（元）与书的本数x（本）
B．xy=7
C．当k=-1时，式子y=（k-1）xk2-2中的y与x
D．小亮上学用的时间x（分钟）与速度y（米/分钟）
A、书的单价为12元，售价y（元）与书的本数x（本），此时y=12x，y与x成正比例，正确；
B、y=
，符合反比例函数的定义，错误；7 x
C、当k=-1时，y=-
符合反比例函数的定义，错误；2 x
D、由于路程一定，则时间和速度为反比例关系，错误．
故选A．
There was once a farmer who lost his watch in his barn ( 仓库 ). The watch was only cheap but it was very ________ to him because it was a present from his father. After ________ the barn for a long time ,he gave up and asked for ________ from a group of children playing nearby. He promised them that the person who ________ the watch would be rewarded ( 奖赏 ). Hearing this , the children hurried inside the barn at once . They searched ________ but still could not find the watch . Just when the farmer was going to give up, a little boy went up to him and asked to be given another ________. The farmer looked at him and thought , “ Why not ? ________, this kid does look honest .” So the farmer sent the little boy back to the barn. After a while the little boy came out with the watch in his hand ! The surprised farmer asked the boy how he ________ where the rest had failed. The boy ________ , “ I did nothing but sit quietly and listen for the sound of the watch .” This shows us that sometimes a peaceful mind can think _______ than an excited one .
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