It is usually warm in my hometown in March, but it ______ be rather cold sometimes.
A:must
B:can
C:should
D:would
某商品销售量y(件)与销售价格x(元/件)负相关,则可能作为其回归方程是( )
若等差数列an的前5项和S5=25,则a3等于( )
张朋将连续10天引体向上的测试成绩(单位:个)记录如下:16,18,18,16,19,19,18,21,18,21.则这组数据的中位数是____.