An example of gene therapy is

• A
  Production of antibodies and vaccines in transgenic plants like banana and tomato
• B
  Delay in flower senescence and fruit ripening in Flavr Savr transgenic tomatoes which have longer shelf life
• C
  Introduction of the gene for the synthesis of $ADA$ (adenosine deaminase) into a person suffering with $SCID$
• D
  Transfer of nitrogen fixing genes ($nif$ genes) into plants that are unable to fix atmospheric nitrogen,example cereals