61. The fundamental difference between materials and energy in an ecosystem is that
(A) energy is cycled through ecosystems; materials are not.
(B) energy can be converted into materials; materials cannot be converted into energy.
(C) materials can be converted into energy; energy cannot be converted into materials.
(D) ecosystems are much more efficient in their transfer of energy than in their transfer of materials.
(E) materials are cycled through ecosystems; energy is not.