What Was the Latest Technological Addition to Seafloor Mapping, Developed

Multiple Choice

What was the latest technological addition to seafloor mapping, developed in response to mapping the ocean floor for national security, resource development, and directing seabed cable and pipeline crossings?

A) fleets of remotely telemetered, miniature drifter buoys
B) swath echo sounding by mechanical multi- beam sonar
C) walking it off one step at a time by the "Pirates of the Caribbean"
D) airborne sounding methods, by overflying the oceans