如图所示,用控制其他因素不变进行探究物体的沉浮和物体轻重的关系。
圆的半径为r,圆的面积S与半径r之间有如下关系:S=πr2.在这关系中,常量是____ 变量是____ .
Harriet is lost and her parents are really ___________ her.