Which of the following is NOT a way in which we map and investigate the seafloor?

A) bouncing sound waves from a ship off the bottom
B) drilling holes into the seafloor from ships
C) using satellites to observe the sea surface
D) conducting seismic surveys to investigate rock layers
E) we use all of these techniques

All of the methods listed (A through D) are indeed used to map and investigate the seafloor. Bouncing sound waves off the bottom (sonar), drilling holes, using satellites to observe sea surface anomalies that hint at seafloor features, and conducting seismic surveys are all techniques employed in oceanography and marine geology.