Ocean acoustic tomography (OAT) is extensively used for:

Correct option is C

Correct Answer: (c) Ocean current studies
Explanation:
→ Ocean Acoustic Tomography infers large-scale ocean properties (temperature, currents) by measuring acoustic travel times between moored or mobile sources and receivers.
→ Changes in travel time reflect variations in sound speed caused by temperature and current fields, enabling current mapping.
Information Booster:
→ OAT provides synoptic, basin-scale measurements complementary to point sensors and satellites.
Additional Information (Other Options):
(a) Depth: sonar bathymetry is used instead.
(b) Salinity: affects sound speed but OAT infers combined temperature/current signals; salinity alone is not the main target.
(d) Ocean sound studies: passive acoustics is used for sound; OAT is an active, diagnostic technique.