A:①③
B:①④
C:②③
D:②④
The Third China-South Asia EXPO was held in Kunming June 12th to June 16th.
小周在日记里写道:“放学时,铃声是悦耳的;考试时,铃声是紧张的;思考时,铃声是刺耳的。”这说明( )
我校数学教研组有25名教师,将他们的年龄分成3组,在24~36岁组内有8名教师,那么这个小组的频率( )