In an ecosystem, plants are autotrophs. the term autotroph means that plants are capable of changing sunlight into sugar. in other words, plants are

In other words, plants are the producers of the biosphere in the ecosystem. they use the process of photosynthesis to use light energy and inorganic carbon dioxide to be fixed into sugar, such that it contains stored chemical energy and is consumed by other organisms. 

Edit the post so i can see the letters for each answer, and increase the points required so i'd be able to answer it.

Ithink your answer is d