A:take it away
B:take them away
C:take away it
D:take away them
元素
Na
Mg
Al
H
C
O
Cl
电负性
0.9
1.2
1.5
2.1
2.5
3.5
3.0
①Na和Cl ②Mg和Cl ③Al和Cl ④H和O
⑤Al和O ⑥C和Cl
如图所示,两块三角板的直角顶点O重叠在一起,且OB恰好平分∠COD,则∠AOD的度数是____度.