如图所示，竖直向上抛出的小球重12 N ，请在图中作出小球所受重力的示意图。
A neighbour helped to keep our dog. It _____ while we were on holidays. [ ]
A. was taken care
B. took care of
C. was taken care of
下列抽样方法中，适用于控制测试的是（）。
A.货币单元抽样
B.差额法
C.属性抽样
D.变量抽样
