矿产品的价格由（）决定
A、劣等矿山
B、中等矿山
C、优等矿山
D、市场决定
参考答案：A
Tony used to _______ to school, but he is used to _______ to school now. [ ]
A. walk; taking a bus
B. walked; took a bus
C. walk; take a bus
建立近代警察制度较早的国家是( )
A．法国和德国
B．美国和英国
C．法国和英国
D．中国和日本
