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

Scientists have succeeded in culturing meristems of:

Arrange the following steps of somatic hybridisation in a correct sequence.
$A$. Digestion of cell walls.
$B$. Isolation of naked protoplasts.
$C$. Fusion of protoplasts to get hybrid protoplast.
$D$. Isolation of single cells from two different varieties of plants.
$E$. Growing of hybrid protoplast to form a new plant.
Choose the correct answer from the options given below:

Viral infection is usually absent in

The plant material which is widely used in the preparation of culture medium is

What does cellular totipotency demonstrate?