He usually exercises_____half an hour.
A:in
B:on
C:for
D:at
(I)求函数f(x)的值域;
(II)已知锐角△ABC的两边长分别是函数f(x)的最大值和最小值,且△ABC的外接圆半径为 324 ,求△ABC的面积.
若代数式1x+2有意义,则实数x的取值范围是( )
January is the ____(one) month of a year.