如图,一只蚂蚁沿边长为a的正方体表面从顶点A爬到顶点B,则它走过的路程最短为( )
A:3 a
B:(1+ 2 )a
C:3a
D:5 a
The little boy ____ ____ ____ speak when he was two years old.
副热带高压控制下的地区的天气特征是( )