Let's look at each answer in turn.
A. It can't be the answer. The reason is that the constant amount increases the wage year on year, so the wage is getting bigger but the increment is becoming a smaller fraction, or percentage, of the wage as time goes on.
B. This can't be the answer even though the increment itself is increasing. The percentage increase isn't in step with this. 0.50/13.50=3.7% approx. The wage is $14/hr. Next year the percentage is 0.75/14=5.4%, so the percent increase is not constant.
C. This is the correct answer because the wage rises by $2, which is 2/20=10% increase. Next year the increase percent is 2.20/22=10%. That's a constant percent increase.
D. This can't be correct if C is correct. Let's see what we've got. 0.75/15=5%; 1.75/17=10.3%. Not a constant increase.