常用的选矿方法有几种？
参考答案：
一般常用的选矿方法有三种即；浮选法、磁选法、重选法。
股票上涨为正，某种股票第一天上涨0.3元，应表示为（ ）元，第二天下跌0.10元，应表示为（ ）元。
Lee Pickett, CFA. a well-known and respected analyst, follows the computer industry and does research about types of measurement scales. Pickett categorizes a group of stocks into quartiles based on historical rate of returns. Pickett's approach is most consistent with which type of the following measurement scales（）
A. Nominal.
B. Ratio.
C. Ordinal.
