The answer is b
The slope of the graph is 1/3; it rises by 1 every 3. Rise/run = 1/3
The line is solid, and not dotted, so you know that the sign for the inequality is greater than or equal to, or less than and equal to.
Because the graph opens upwards, y>f(x)
The y-intercept is -1
When you combine all these factors, you get the function y >= (1/3)x - 1