选项
A.
A.$ f : N rightarrow N, f(x)=x^{2}+2 $
B.
B.$ f : N rightarrow N, f(x)=x(bmod 3) $
C.
C.$f : N rightarrow{0,1}, quad f(x)=left{begin{array}{ll}{1} , {x in 偶数集} {0} , {x in 奇数集}end{array}right. $
D.
D.$ f : R rightarrow R, quad f(x)=2 x-5 $
正确答案：D