Answer would be B. Earthquakes happen most of the time when a volcano is about to erupt.
Ok that is not true at all it serves as a physical border between Mexico and the United States
It is impossible to build a drainage system on the outside of the Sao Francisco river as buildings are built on the outside of the foundation.
The Subarnarekha is developing a small drainage system.
The Amazon basin is the largest drainage basin in the world.
The Urugay drainage system includes the greater part of southeastern Brazil, Paraguay, southeastern Bolivia and northern Argentina
So i would suggest putting the Amazon as it is the most common known and largest. Remember to use geographical terms!
Please be more descriptive.
