Question
In an ecosystem :
(i) the flow of energy is unidirectional
(ii) the flow of materials is unidirectional
(iii) the flow of materials is cyclic
(iv) the flow of energy is cyclic.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (i) and (iii)