题目

Mr. Keller ______ forty cigarettes a day until he gave it up. A. had smoked             B. smokes                C. have smoked              D. smoked 答案：D如图，冰漂浮在水面上，沉于酒精中，则下列说法正确的是 A．冰受到水的浮力大于冰的重力大小B．冰受到水的浮力等于冰的重力大小 C．冰受到酒精的浮力等于冰的重力大小D．冰受到酒精的浮力大于冰的重力大小