Answer:
b. Costs that were incurred in the past and cannot be changed.
Step-by-step explanation:
Sunk Cost -
It is the cost which has incurred in the previous time and can not be recovered , is known as sunk cost .
The sunk cost is not thought during the process of decision making of any presently running project , being a non recoverable cost .
Hence , from the given option the correct statement for sunk cost is ( b. ) .