Consider the following statements. (i) An ecosystem is a functional unit of nature and comprises abiotic and biotic components. (ii) Abiotic components are organic materials. (iii) Biotic components are producers, consumers and decomposers. (iv) Energy flow is bidirectional. Which two statements are correct?

• A. (i) and (ii)
• B. (ii) and (iv)
• C. (iii) and (iv)
• D. (i) and (iii)