Final answer:
Tectonic plates are segments of the lithosphere floating on the mantle, moved by convection currents within the mantle. The correct options are B and D.
Step-by-step explanation:
Under the theory of plate tectonics, the plates themselves are large segments of the Earth's crust and upper mantle, collectively known as the lithosphere, that are neither solid and immovable nor fixed in position.
Rather, these tectonic plates are floating on the mantle and move around the globe at a rate of millimeters to a few centimeters per year.
The movement of these plates is powered by the slow convection currents within the mantle, where heat from the interior causes the upward flow of warmer material and the sinking of cooler material.
Hence, Options B and D are correct.