The correct answer is A mass of undifferentiated cells.Concept:Tissue culture:?It is the cultivation of plant cells, tissues, or organs on specially formulated nutrient media.Under the right conditions, an entire plant can be regenerated from a single cell.Explanation:The process of tissue culture:The explant is removed from the parent plant.Then, the totipotent cells are extracted from the explant.These cells are given nourishment, consisting of sucrose, vitamins, and micronutrients with the plant hormones like auxins, cytokinin, etc.The cells divide and develop as a callus, and the callus further divides and grows as small plantlets.Once the plantlets are grown, they are moved to the nurseries for further growth.Important terms:Explant The part of the plant body was removed for the extraction of cells.Totipotency cellThe capability of dividing and growing into a whole plant.CallusThe undifferentiated mass of cells.