What is isostasy dependent on a balance between

a the downward push of the continents and upward push of the mantle
b the downward push of the ocean floor and upward push of the continents
c the downward push of the ocean floor and upward push of the mantle
d the downward push of the continents and upward push of the mantle

Option (A) and (D)

Explanation: Isostacy is the gravitational state of equilibrium in which a block sinks down due to the addition of materials and also the same block rises up if materials are eroded.

          In terms of our earth, the gravitational force is responsible for the sinking or down-pushing of the continents, and the bouyancy forces in the mantle is responsible for the uplifting of the continents.

two charges are fixed in place on the x-axis as shown. the charge at x = 0 is negative and has magnitude q = 2 μcoulombs (1 μcoulomb = 10-6 coulombs). the charge at x = d, (d = +12 cm), is positive and has magnitude q = 4 μcoulombs. find a point x = xo along the x-axis at which the electric field is zero.