The condition of equilibrium that results in the displacement of the mantle by the continental and
oceanic crust is known as
a. isostasy.
b. erosion.
c. root rebound.
d. topography

Isostasy is the condition of equilibrium that results in the displacement of the mantle by the continental and oceanic crust.
The answer is A. Isostasy.
Isostasy is also known as standstill.It is the condition that makes earth's crust and mantle to float dependin on the thickness of the roots.

Iam pretty sure it is c. 2000 bce

Sonar is an application of the doppler effect used by submarines.  this test was on k12.