The correct option is C Iodine
Seaweeds are among the most potent accumulators of iodine. Kelps of the Laminaria genus were identified as a major iodine source. Iodine is found at low concentrations throughout the ocean waters, many types of seaweed accumulate the element in very high levels. It has been suggested that seaweeds could be an important route to transfer iodine to the atmosphere.