Ecological cycling of which of the following in not assisted by microorganisms

Answer: Option A

Ecological cycling of Lead is not assisted by microorganisms.
The lead cycle is the biogeochemical cycle of lead through the atmosphere, lithosphere, biosphere, and hydrosphere, which has been influenced by anthropogenic activities.
Anthropogenic activities have accelerated lead mobilization to the environment. The majority of anthropogenic lead comes from non-ferrous metal manufacturing plants, mining and smelting of ores, stationary and mobile fossil fuel combustion platforms, and lead batteries.