Answer:
A) Iron
Step-by-step explanation:
Iron is the element that is important for the chemotrophs in the ocean because the plants used this iron for making different compounds necessary for plant's survival. Chemoautotrophs uses inorganic energy sources, of which hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia are most important. Chemoautotrophs are organisms that are able to use chemical energy obtained through the oxidation of reduced compounds.