Final answer:
The area is legally described as the Exclusive Economic Zone (EEZ) of California. So the correct answer is Option B.
Step-by-step explanation:
The area legally described by the oil field discovered 30 kilometers away from the coast of California would be the Exclusive Economic Zone (EEZ) of California.
The EEZ is a zone extending 200 nautical miles (about 370 kilometers) from the coastline, within which the coastal state has special rights over the exploration and exploitation of natural resources, including oil and gas. The coastal state has the exclusive right to exploit and manage the resources within its EEZ.
In this case, since the oil field is discovered within 200 nautical miles from the coast of California, it falls within California's EEZ, making it the legally designated area.