下列哪一类变量用于划分社会经济群体（）。
A.国家/地区/城市
B.对待产品的态度
C.收入/职业/教育
D.季节性购买
参考答案：C
Tom goes to school ________ every day. [ ]
A. by a bus
B. by his bike
C. by buses
D. on foot
