What is the process of transformation? infecting bacteria with bacteriophages copying foreign dna into rna adding foreign dna to a bacterial cell causing mutations in viral genetic material

The correct answer is adding foreign DNA to a bacterial cell.  

Transformation is a process in which genetic material in the form of deoxyribonucleic acid (DNA) is transferred into the recipient bacteria. It can occur between two bacterial cells or it can be induced in laboratory procedures (making the cell permeable to foreign DNA by exposing it to special conditions).

infecting bacteria with bacteriophages is called transduction.