从总体中随机抽取若干群为调查单位,然后对每个群里的所有对象进行检查称之为()
A.单纯随机抽样
B.系统抽样
C.分层抽样
D.整群抽样
E.多级抽样
参考答案:D
下列属于经络生理功能的是()
A.沟通表里上下,联系脏腑器官
B.通行全身气血
C.濡养脏腑组织
D.感应传导作用
E.调节功能平衡
At all angles of inclination, the metacenter is().
A.vertically above the center of buoyancy
B.vertically above the center of gravity
C.at the intersection of the upright vertical centerline and the line of action of the buoyant force
D.at the geometric center of the underwater volume