we can use the vertical line test
if we can draw a vertical line that passes through the points twice, then it is not a function (remember, every x has 1 y coresponding)
we can't draw any vertical line
this is a floor function actually
the empty circles are like the > or < sign
the filled in circles are like ≤ or ≥
this is a function and it is one-to-one because every x goes with 1 y
da answer is B
