which of the following describes a one-to-one function?
A. 5x-1: x<-2
y= x-9: x>_ -2
B. y= |x|
C. y=[ [x] ]
D. 4: x<0
y= 5: 0<_x<_2
6: x>2

when i use <_ its less than or equal to. (not sure how to type that)
and >_ is greater than or equal to.

A is a system of equations
D is a system of equations