下列函数中，最小正周期为π的奇函数是（ ）
A：y=sin（2x+π2）
B：y=cos（2x+π2）
C：y=sin2x+cos2x
D：y=sinx+cosx
—I think students should have mobile phones to call their parents.
—________. They often use them to play games instead.
已知x-3y=-3，则5-x+3y的值是（ ）
