The correct option is C Nearly 240 sq km
Explored area is the area that has been explored or colonised by organisms. It is different from the total area, in that regions that are not colonised or have not been explored do not form part of the explored area. In this hypothetical scenario, since fossils were found in regions I and II, we can presume that the organisms colonised these two regions, and that they were not able to access the other regions of the island. Region I is about 160 sq km and II is about 80 sq km. Therefore the total explored area would be about 240 sq km.