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 B Both apical and axillary meristems
Tissue culture is the technique of growing plant cells, tissues or organs in a sterile culture medium under controlled environmental conditions.

If the parent plant considered for tissue culture is infected with virus, then offspring raised from explants derived from its roots, shoots, leaves, twigs, anthers, etc have high chances of being infected as these parts might harbour the virus.

However, viruses are unable to grow within the meristematic cells of the root tips and shoot tips as these cells undergo very rapid cell division. Thus, the virus is unable to complete its life cycle and multiply within these cells. Thus, apical meristems or axillary meristems can be used as explants to raise virus free plants by tissue culture. Such a culture using explants containing meristems is known as meristem culture.

So, the correct answer is option C.