—_______does your father play tennis after work?
—Every Tuesday and Thursday.
A:How often
B:How soon
C:Where
D:Why
历史是复杂的。有时吸取前人的历史教训会导致新问题的产生。下列史实能佐证这一看法的是
如图所示的圣诞帽呈圆锥形,其母线长为2,底面半径为1,则它的侧面积为