题目: 下列关于力与运动的说法中正确的是()A.书放在水平桌面上受到的支持力,是由于书发生了微小形变而产生的B.以地面为参考系时,同步卫星是静止的C.摩擦力总是阻碍物体的运动D.在匀减速直线运动中,加速度一定是负值 答案: 参考答案:B
题型:选择题 The traffic accident wouldn’t have happened yesterday,but the driver _________ really careless.A.had been B.isC.were D.was 查看答案
题型:单项选择题 Questions 14-22 ·Look at the ten statements for this part. ·You will hear apassage about "Credit Cards History ". You will listen to it twice. ·Decide whetheryou think each statement is right(R), wrong(W) or not mentioned(NM). ·Markyour answers on the Answer Sheet.The early cards required payment within a month.A.RightB.WrongC.Not Mentioned 查看答案
题型:单项选择题 相同质量的碳酸钠,基本单元为Na2CO3的物质的量和基本单元为1/2Na2CO3的物质的量之间的关系是()。A、n(Na2CO3)=n(1/2Na2CO3)B、n(Na2CO3)=2n(1/2Na2CO3) C、2n(Na2CO3)=n(1/2Na2CO3)D、不确定 查看答案