The total amount of profits of Brandeburgh Bicycle Company

The total amount of profits of Brandeburgh Bicycle Company (BBC) must have increased dramatically over the last 5 years. After BBC developed a light and strong new material for its bicycles, total sales increased to twice what they were 5 years ago. Nevertheless, sales of certain types of bicycles, for which the new material is not used due to its high cost, have remained constant or, as is the case with bicycles for children, have decreased. Four years ago, sales of childrens bicycles constituted 30 percent of the total bicycle sales of BBC, and now they constitute barely 20 percent of all BBCs sales.

Which of the following must be assumed in order for the assertion that the total amount of profits of BBC has increased dramatically over the last several years to be true?
(A)Increased sales always result in increased profits.
(B)BBC bicycles are not significantly more expensive than 5 years ago.
(C)Over the last 5 years, total sales of BBC racing bicycles did not decrease by more than 70 percent.
(D)Over the last 5 years, the average amount of profit gained by BBC per bicycle sale has decreased by less than 50 percent.
(E)The proportion of bicycle market occupied by bicycles of BBC has not decreased over the last 5 years.

I am finding the argument difficult to understand appreciate if some one could explain. I will post the OA soon.