Question

think: why might shortages lead to black markets?

Explanation:

When shortages occur, the quantity demanded of a good far exceeds the quantity supplied through legal, official channels. This unmet consumer demand creates an incentive for suppliers to sell the scarce goods outside of regulated markets, often at prices higher than the legal or controlled price. These unregulated, off-the-books markets emerge to satisfy the unfulfilled demand, as consumers are willing to pay more to access the scarce goods they need or want, and suppliers can profit from the price discrepancy.

Answer:

Shortages create unmet consumer demand for scarce goods. Since legal supply cannot satisfy this demand, suppliers emerge to sell these goods in unregulated (black) markets at above-market/legal prices to profit, while consumers are willing to pay more to obtain the scarce items, leading to the formation of black markets.