To obtain virus free healthy plants from a diseased one by tissue culture technique, which part/parts of the diseased plant will be taken?

The correct option is D Both apical and axillary meristems

Definition of tissue culture
Tissue culture is a technique where parts of a selected plant are aseptically transferred to an appropriate culture medium containing the required growth factors, leading to the formation of an entire plant.

Advantage of tissue culture
As a result of tissue culture, large amounts of high quality plants can be produced in a short duration of time. Virus-free plants can be generated from virus-infected parent plants, through the method of meristem culture, where the meristem of the parent plant is used as an explant for tissue culture.

Role of meristem in producing virus free plants
Viruses are obligate parasites that cannot survive outside of the host cell.
Meristems are regions found in the growing point of a plant that have actively dividing cells (meristematic cells).Virus needs a host replication mechanism to replicate and it divides at a slower rate. It cannot multiply inside an actively dividing cell. Thus, meristematic tissues in both apical and axillary buds are free of virus and can be used to micropropagate virus-free plants.