What percentage of the world's population lives on or within 260 kilometres of a coastline? 

A)  about 50% 
B)  about 40% 
C)  about 30% 
D)  about 20%

According to a study conducted by the United Nations, roughly 40% of the world's population lives within 100 kilometers (62 miles) of a coastline. This number increases to around 60% when looking at populations within 200 kilometers (124 miles) of a coast. However, the question specifically asks about a distance of 260 kilometers (161 miles), and no precise statistics could be found for that exact range. Therefore, the closest answer is B, which is the closest percentage to the 60% mentioned for populations living within 200 kilometers of a coast.