C. the Spratly island and Taiwan claimed it
The unit of measure used to determine an absolute location on a map or globe is called "degrees" of longitude and latitude.
"Shallow‐focus earthquakes occur along transform boundaries where two plates move past each other. The earthquakes originate in the transform fault, or in parallel strike‐slip faults, probably when a frictional resistance in the fault system is overcome and the plates suddenly move."
https://www.cliffsnotes.com/study-guides/geology/earthquakes/earthquakes-and-plate-tectonics