'Wolbachia method' is sometimes talked about with reference to which one of the following?

The Wolbachia method involves introducing naturally occurring bacteria into *Aedes aegypti* mosquitoes to significantly reduce their capacity to transmit viral diseases such as Dengue, Zika, and Chikungunya. The core concept tested is the application of biotechnology and biological agents for vector control in public health. While options like (d) concerning biochar are frequent UPSC themes, they relate to thermo-chemical biomass conversion and carbon sequestration rather than the microbiological prevention of infectious diseases.