Dont wanna sound desperate but pls pls pls
this is the theory that states that the continents were once connected in one large land mass and have since moved apart.
crust tectonics
plate tectonics
continental shelf
continental drift

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.

answerparathyroid gland;

the correct answer is primary!