Explanation:

Black carbon is a short-lived pollutant. It is found worldwide but its presence and impact are particularly strong in Asia.

• PM2.5 consists of black carbon, often called soot, and polycyclic aromatic hydrocarbons, among others.
• A study in Italy correlated the incidence of coronavirus cases with increase in PM2.5 levels.
• Another recent study concluded that the COVID-19 virus piggybacks only black carbon emitted during biomass burning, and not all PM2.5 particles.
• It also found that the concentration of black carbon directly corresponds to the speed at which infections spread after the onset of winter and stubble burning period and then reduced with a declining trend in BC with reduction in stubble fire counts.

Hence only statements 1&2 are correct.