Energy flow in ecosystem is

The correct answer is A. Unidirectional.

Energy flow in an ecosystem is unidirectional, meaning that it flows from one organism to another in a single direction. This is because energy is always lost as heat when it is transferred from one organism to another. As a result, the amount of energy available to each successive trophic level decreases.

Option B is incorrect because energy flow is not bidirectional. Energy is not transferred back and forth between organisms in an ecosystem.

Option C is incorrect because energy flow is not multidirectional. Energy is not transferred in all directions in an ecosystem.

Option D is incorrect because energy flow is unidirectional.