The correct answer is B Subduction. Subduction is the process by which an oceanic plate gets dragged under another plate and is eventually destroyed in the mantle. Subduction occurs at convergent margins where two oceanic plates collide or an oceanic and Continental plate collide. Oceanic crust is made of mainly of silica and magnesium which is heavier or denser than continental crust which is composed mainly of silica and aluminium.
The subducting plate melts producing excess magma giving rise to volcanoes along these margins.
It was caused by widespread disconnect with the French monarchy and the poor economic policies of King Louis XXI
You would take a ruler and measure the amount of centimeter or inches between the two places. Then measure the scale. If the scale was 50 miles and 1 inch and the two points were 2 inches apart. The places would be 100 miles apart because 50*2=100