A squirrel standing on a branch shoots an acorn toward a hole in the tree. To determine how the potential energy of the acorn changes in relation to the earth, the position of what two objects must be considered?

a
The position of the acorn and the earth

b
The height of the branch and the position of the acorn

c
The position of the acorn and the width of the hole in the tree

d
The position of the squirrel on the branch and the earth