如图所示，在一粗糙水平面上有两块质量分别为m1和m2的木块1和2，中间用一原长为l、劲度系数为k的轻弹簧连接起来，木块与地面间的动摩擦因数为μ.现
下列化学方程式中，不能用离子方程式，Ba2++SO42-=BaSO4↓表示的是（ ） A. Ba(NO3)2+Na2SO4=BaSO4↓+2HNO3 B. BaCl2+H2SO4=BaSO4↓+2NaCl C. Ba(OH)2+K2SO4=BaSO4↓+2KOH D. Ba
Linda often asked Luke to dinner. Linda loved Luke, but Luke loved Linda’s cooking, not Linda herself. Linda accepted that for the time being. But she felt that, with enough meals and enough time
in the eighth century, the city has long been a cultural, artistic and religious center. A. To found B. Founding C. Founded
（ ） , I think, and the problem could be settled. A．If you don’t doubt your efforts B．So long as you keep up your spirits C．Making great efforts
如图所示，一位母亲推着婴儿车行走，当前轮遇到障碍物时，母亲向下按扶把，若把婴儿车视为杠杆，这时杠杆的支点是_____________；当后轮遇到障碍物
微山湖是江北最大的淡水湖，有“日进斗金”的美誉，下列关于微山湖的描述中属于生态系统的是（ ）A．微山湖中的水B．微山湖中的荷花C．微山湖中
民国时期《申报》有如下记载：“梳一东洋头，披件西式衣，……宣读婚约，互换约指，才一鞠躬，即携手而归，无傧相催请跪拜起立之烦。”该现象
