如右图所示，一个物体A恰好静止在斜面上，现用一竖直向下的外力F作用于A，设最大静摩擦力等于滑动摩擦力，下列说法中正确的是（ ）
A．物体A所受的摩擦力增大
B．物体A对斜面的压力可能保持不变
C．无论F怎样增大，物体A总保持静止
D．当F增大到某一值时，物体可能沿斜面下滑
AC
物体A恰好静止在斜面上
，施加压力后，压力和摩擦力都增大，
，物体仍保持静止。答案选AC。
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| The telephone rang. Mrs. Green went to 1 it. 2 was Vicky, her friend. Mrs. Green asked Vicky to come and have 3 with her and her family that evening. 4 a quarter to six, Mr. Green came back home with his children. He saw his wife 5 the window of the kitchen. She was 6 "What's 7 ?" he asked. "I've made a terrible mistake, Jim," She said "I've asked Vicky to come and have dinner with 8 this evening." "Well, that's 9 to worry about." Mr. Green said. "We should have a happy 10 together. We haven't seen her 11 a long time." "But I've just found that there isn't enough food in the house. I 12 you to get some meat on your way home three days ago and you forgot it." "Oh, my dear!" said Mr. Green. He stood still 13 his family. Suddenly he walked out of the house and ran 14 his car. He found some 15 in the car. It had been there for three days. | ||||
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