Which is the graph of the step function f(x)? f(x) = StartLayout Enlarged left-brace 1st row 1st column negative 1 2nd column x less-than negative 1 2nd row 1st column 0 2nd column negative 1 less-than-or-equal-to x less-than-or-equal-to 1 3rd row 1st column 1 2nd column x greater-than 1 EndLayout