Biolistics (gene-gun) is suitable for: Transformation of plant cells; Disarming pathogen vectors; Constructing recombinant DNA by joining with vectors; DNA finger printing.

The correct option is A Transformation of plant cells. Biolistic gun or gene gun method initially developed to transfer the gene in plant cell directly. It is a method involving the transfer of genes to the plants without the use of any vectors (plasmid etc). Thus, the correct answer is option A.