The introduction of T-DNA into plants involves
altering the pH of the soil, then heat shocking the plants
exposing the plants to cold for a brief period
allowing the plant roots to stand in water
infection of the plant by Agrobacterium tumifaciens
The correct option is D infection of the plant by Agrobacterium tumifaciens
Agrobacterium tumefaciens is a pathogen of several dicot plants. It is used for the gene transfer in higher organisms. It is able to deliver a piece of DNA known as 'T-DNA' to transform normal plant cells into a tumor and direct these tumor cells to produce the chemicals required by the pathogen.