Answer:
A. Ridge push from the asthenosphere is responsible for isostatic uplift.
Step-by-step explanation:
Ridge push otherwise sliding plate or gravitational sliding force is a force that causes plate tectonics motion at the mid-ocean ridge. The movement pushes the old plate material back into the subduction zone or the asthenosphere.
The uplift is the process of slow rise of the land which result in formation of mountains, the isostatic uplift refers the rise of the crust.
The force, however, acts on the entire ocean plate and not only on the ridges due to gravitational force. It is called ridge push because earlier models of plate tectonics during simulations showed the up welling of the magma during spreading of the sea-floor at mid-oceans ridges which cause plate to diverge.