—Before he went on the stage,he took a deep ______ .
—He was too nervous.
A:breath
B:smile
C:voice
在下列各组向量中,能作为表示它们所在平面内所有向量的基底的是( )
已知倾斜角为α的直线l与直线x+2y﹣3=0垂直,则cos(2015π2﹣2α)的值为( )
下图中A,B,C,D四地位于同一纬度,其昼夜温差最小的是( )