I think it is A.burning of fossil fuels
The largest landlocked harbor in the world is B. San Francisco Bay. It is located in Northern California.
Answer:
Vatican City (I know it has city in the name lol)
Explanation
Trust me on this one though haha
The land mass is technically a country because of the Lateran treaty of 1929, which made Vatican city an independent state under the Holy See.
The best answer to go with is b