一个圆锥的母线长是9,底面圆的半径是6,则这个圆锥的侧面积是( )
A:81π
B:27π
C:54π
D:18π
从方框中选择恰当的词或短语并用其正确的形式填空(每个词或短语只能用一次)。
busy; difficult; dream of; be covered live ; arrive in; be away;
row a boat; in one's fifties; out of control ; have a chat with