A:4π
B:3π
C:2π
D:π
地球上最大的生态系统是( )
—Yes. The group leader said we would meet there at half past ten.
已知一次函数y=kx+b﹣x的图象与x轴的正半轴相交,且函数值y随自变量x的增大而增大,则k,b的取值情况为( )