The correct option is D meristem culture
Meristem culture is the in vitro culture of a generally shiny, special dome-like structure measuring less than 0.1mm in length and only one or two pairs of youngest leaf primordia, most excised from the shoot apex.
It is possible to produce disease-free plants through tissue culture. Apical meristems in the infected plants are generally either free or carry a very low concentration of the viruses. The various reasons attributed to the escape of the meristems by virus invasion are: Meristem –tip cultures has also enabled plants to be free from other pathogens including Viroids, mycoplasmas, bacteria and fungi. Therefore, the main objective of shoot-tip and meristem –tip culture is the production of disease-free plants through micropropagation.