All of these are human activities that threaten biodiversity except  

A. Various fertilizers are used in agriculture which contain nitrogen as a key component. Runoff from agricultural land causes the release of excess nitrates.

B. Over harvesting of plants and animals for profit by the mankind has resulted into extinction of various species.

C. Overuse of herbicides kills the soil microflora and other microorganisms also.

D. Habitat preservation is not a threat to biodiversity as it will save the species.

E. Ozone has depleted due to various human activities like CFCs and due to this, excess ultraviolet rays can reach the earth and cause various problems to biodiversity.

Hence statement C is incorrect.

So, the correct answer is 'Habitat preservation'.