Is the use of sound waves to detect and measure objects underwater. a. gps b. ostm c. sonar d. gis

It's option C. Sonar.

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.

Can you maybe send me a screen shot of the map? it would really me you. : )