World biodiversity day is
Correct option is D. 22$$^{nd}$$ may
Biodiversity day or the Biological diversity day is a UN sanctioned day celebrated internationally. It addresses the promotion of biodiversity issues. Currently, the day is held on May 22. Earlier, it was held on December 29 to celebrate the day in which the Convention on Biological Diversity came into action.
So, the correct answer is '22 May'.