对以下八位帝王称号归类正确的是 [ ]
A、谥号：周武王、隋文帝
B、庙号：唐太宗、永乐帝
C、尊号：商纣王、秦始皇
D、年号：汉武帝、康熙帝
答案：A
I just don’t understand ________ that prevents so many children at school from being as happy as one might expect.
A．what it is
B．what it does
C．what is it
D．why is it
电线下吊一电灯，下列哪一对力是电灯所受的平衡力（ ）
A．灯所受重力和电线对天花板的拉力
B．灯对电线的拉力和天花板对电线的拉力
C．灯所受重力和电线对电灯的拉力
D．灯所受重力和天花板对电线的拉力
