从空中某一点先后静止释放甲、乙两个物体，不计空气阻力，讨论甲、乙两物体在空中下落时的情况，下列说法中错误的是（ ）
A．甲、乙两物体的间距将随时间成正比增大
B．甲、乙两物体的运动速度之差随时间成正比增大
C．甲、乙两物体的运动速度之差恒定不变
D．以甲为参照物，乙做匀速直线运动
A、设乙运动的时间为t，则甲运动时间为t+△t；
则两球的距离x=
g（t+△t）2-1 2
gt2=gt•△t+1 2
g（△t）2，可见，两球间的距离随时间推移，越来越大，故A正确；1 2
B、C、设乙运动的时间为t，则甲运动时间为t+△t；两球速度之差为：△v=g（t+△t）-gt=g•△t，所以甲乙两球速度之差保持不变，故B错误，C正确；
D、由BC选项分析可知，甲的速度与乙的速度之差是固定的，为g•△t，故以甲为参照物，乙以速度g•△t向上做匀速直线运动，故D正确；
本题选错误的，故选B．
Mrs. Evens was home from work. She had just gone into the kitchen to make the afternoon tea _36_ she saw a mouse running around on the kitchen floor. She 37 and jumped up on the table. As soon as the mouse had disappeared, she jumped off from the 38 , rushed out of the kitchen, _39 her coat, ran out of the house and got on a bus 40 was going into the town. There she hurried into a shop and 41 a large mouse-trap（捕鼠夹）. She wanted to put 42 to this mouse as quickly as 43 . When she got home 44 the trap, she realized that she had forgotten 45 any cheese （奶酪）to put in it. She searched everywhere 46 there was 47 in the house. It was too late to buy any because now all the shops were 48 . She wondered what to do. In the end she 49 a clever idea. She took a pair of scissors and cut a picture of a piece of cheese 50 a magazine. Then she put the picture in the trap 51 a piece of cheese. The next 52 Mrs. Evans came down to the 53 and went straight away to the place 54 she had put the trap. She wanted to see if her plan had 55 . The picture of the cheese had gone and in its place was a picture of a mouse.
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