The Answer is second option (Tombouctou).
Answer: B - help map the ocean floor
Explanation: GPS which is an acronym for Global Positioning System is a global satellite based location and navigation system owned by the US Government. It was first used by the US Air Force in 1978. It's main purpose is to show a GPS user location and time information from anywhere on earth, where there is an unobstructed line of sight from the precise location to 4 or more GPS satellites. GPS is commonly used on land (obviously through every day use like when you use an uber) and in the air (pilots use GPS signals when they fly).
GPS can be used to track pets if there's a tracking device on their collars.
GPS is also used in taxis and can be used to track a cab after a hurricane.
Ordinary people can use GPS to collect information for scientists - an example of this would be taking a new undefined route on Google maps therefore adding to their archive of known routes/areas.
However GPS signals cannot penetrate water - sea water especially. Hence the answer is B
