Study the given graph and answer the question that follows.

In which year is the percentage increase in the revenue as compared to that in the preceding year the highest?

We know, 

Percentage increase in revenue = $$\frac{Revenue\ in\ current\ year-revenue\ in\ previous\ year}{revenue\ in\ previous\ year}\times\ 100$$

Note : Taking data from the graph given in question,

% increase in Revenue in 2015 = $$\frac{300-260}{260}\times\ 100=15.38\%$$

% increase in Revenue in 2016 = $$\frac{340-300}{300}\times\ 100=13.33\%$$

% increase in Revenue in 2017 = $$\frac{350-340}{340}\times\ 100=2.94\%$$

% increase in Revenue in 2018 = $$\frac{375-350}{350}\times\ 100=7.14\%$$

It is clear that the percentage increase in the revenue as compared to that in the preceding year the highest in 2015.

Hence, option C is correct.