To approximate a scatterplot, we use lines of best fit. Sometimes these aren't lines because the trend may not be linear, like temperature. The average temperature a town tracked monthly would look like a sinusoid. Here though, we can see that this is probably linear. It increases every other year at a near constant rate. Even plugging in numbers gives us near enough values that the others could not compare with. The first function has a problem - it grows too fast. The second equation also has a problem, the slope. The wage is increasing so the function should too. The third is most likely the right one. The fourth does not work because it becomes negative almost immediately.
Through some inductive reasoning, we can say that the most probably line of best fit would be C.