Healthy plants can be obtained from virus infected plants through Tissue Culture by using its :

Meristem

The correct answer is Option (3) → Meristem

Plant tissue culture is based on the special property of plant cells to generate a whole plant, called totipotency. The plant part used in tissue culture is called explant. The nutrient medium provides a carbon sources such as sucrose. inorganic salts, vitamins, amino acids and growth regulators like auxins cytokinins etc. Propagation of thousands of plants in very short duration through tissue culture is called micropropagation. Each of these plants will be genetically identical to the original plant i.e., they are somaclones.

Another important application of the method is the recovery of healthy plants from diseased plants. Although the plant is infected with a virus, the meristem (apical and axillary) is free of virus. Hence, one can remove the meristem and grow it in vitro to obtain virus-free plants. Scientists have succeeded in culturing meristems of banana, sugarcane, potato, etc.