What is the energy source of the convection cells in the earth's mantle?

a.
magma pushing through the crust at hot spots

b.
radioactive decay in the earth's interior

c.
gravity acting on the edge of the plates

d.
the sun's energy heating the crust

The “death throes” of stars are amongst the most complex phenomena in all of astronomy, and the “corpses” of stars amongst the most energetic and exotic objects in existence. beginning at the end of the core helium fusion stage in a star’s life, describe in detail the post-main sequence development of both (a) a 1.0 solar mass star, and (b) a 25.0 solar mass star. in what significant ways do they differ? what role does each of these types of stars play in the "star-gas-star" cycle and the evolution of chemical elements in our galaxy?

What are the three ways that an object can accelerate

Anybody wanna ? (picture included? )