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 meristem is the tissue in plants that contain undifferentiated cells or meristematic cells which are rapidly dividing cells and thus are the virus-free part of the diseased plant. The culture with meristem has enabled the production of disease-free varieties including virus-free healthy plants. Thus, the correct answer is option C.