孟塞尔把研究颜色特性用立体坐标的方法表示出来，称为（）。
参考答案：孟塞尔色立体
位于踝关节横纹中央，当长伸肌腱与趾长伸肌腱之间的穴位是（）
A.中封
B.解溪
C.丘墟
D.商丘
E.冲阳
I didn't come to school yesterday I had to look after my grandmother at home. [ ]
A. because
B. because of
C. since
