A:②③
B:③④
C:①②④
D:①③④
____,____。后之视今,亦由今之视昔。
—I've got a headache.
—No wonder.You in front of the computer too long.
幂函数y=xm2+2m-3(m∈N)在区间(0,+∞)上是减函数,则m=____