Energy flow in an ecosystem begins with

A. Omnivores
B. herbivores
C. Autotrophs
D. Detrivores
E. Carnivores

C. Autotrophs. They take ambient energy (light, heat) to turn biologically unusable molecules into high-energy molecules that then enter the food chain. Plants, consummate autotrophs, turn CO2 into sugar using the sun.

C. Autotrophs -- the primary producers at the base of the food chain.

c