Study the text given below and answer the question that follows it:

Dense, dirty air laced with grease best describes the atmosphere of most Lagos streets. Drive from one corner of this great west African city to another and in no time you will find surfaces lightly dusted, like a soft sprinkling of icing on cakes. Under the half-moons of fingernails, thick grime settles. It’s a scene taken as typically African: polluted, bedraggled, unhealthy. This has only ever been made possible by the exploitation of Africa’s people. This week five west African countries, Nigeria included, announced plans to end the practice of European oil companies and traders exporting “African quality” diesel. “Dirty fuel” has earned the name because it is imported diesel with sulphur levels as high as 3,000 parts per million when the European maximum is 10ppm. To be clear, “African quality” fuel, is fuel not fit for European humans.

Which of the options is not necessarily the underlying assumption of the author in the paragraph above?