The correct answer is: "
considered to be doing business on the black market".
Rationing takes place when a certain market (for example, appartment market) is not in equilibrium and there is an excess of demand hence, the amount demanded of such product is larger than the number of units that are supplied.
If price variations are not allowed under a certian economic system, the price of the product cannot rise and the equilibruim in this market cannot be restored. Therefore, the available units of the product are allocated among the consumers by using a rationing mechanism that establishes certain rules to state which of those consumers would receive the product first, who go next and who cannot have it at all.
If some of the consumers violates the established rules and offers a higher price (which is not allowed), it evidences the emergence of black market practices that circumvent the rationing mechanism.
