Correct option is D
The correct answer is (d) 2020: Covid.
A biological calamity occurs when viruses, bacteria, or other diseases cause widespread illness or death. The Covid-19 pandemic, caused by the SARS-CoV-2 virus, is a textbook case of a biological calamity.
Bhopal Gas Tragedy (1984) was a chemical disaster.
The 2004 Tsunami and the 2009 Aila were natural disasters.