Rapidly dividing unorganised mass of cells in tissue culture is

The correct option is B Callus.
Tissue culture is a growth of cells or tissues separate from the organism in an artificial environment. The process is called as micropropagation in plant tissue culture. In tissue culture, the small piece of plant or animal is used to grow complete individual and those small parts are called as explants whereas complete grown individuals are called clones. The explant initially turns into rapidly dividing unorganised mass of cells on solid or liquid culture and that is called a callus.