Answer: The research team can conclude right away that the cell line is a "cancer cell or a cell that emanates from a tumor cell".
Explanation: 'Density-dependent inhibition is when cell growth has a reached a limited density which in turn will slow down the rate of cell growth because of lack of new 'anchorage' point (new cells to adhere and be in contact with).
'Anchorage Dependence' is the need for cells to be in contact (adherence) with another layer of cells. Cells require anchorage in order to survive.
The reason why the researchers will conclude right away that the cell line is a "cancer/tumour cell" is because normal cells display density dependence inhibition while cancer cells 'proliferate' (increase in number) regardless/independent of cell density.
Normal cells adhere to each other (need to be in contact with each other) and form orderly array of cells while cancer cells do not adhere to cells and can migrate over adjacent cells thereby growing in a disorderly manner.