Consider a Rock Interacting Gravitationally with the Earth, and Choose $20 \mathrm{~m}$

Multiple Choice

Consider a rock interacting gravitationally with the earth, and choose the interaction's potential energy to be zero if the rock is at the ground level. A person standing at the bottom of a well throws the rock vertically upward from $20 \mathrm{~m}$ below ground level. The rock makes it all the way up to $1 \mathrm{~m}$ below ground level before falling back into the well. The total energy of the rock-earth system is

A) negative.
B) zero.
C) positive (in this particular case) .
D) positive (because energy is always positive) .
E) The answer depends on information not specified.