In a housing market with an effective rent ceiling,
a. all landlords gain, and the deadweight loss is borne by the consumers who can't find housing
b. all consumers gain, and the deadweight loss is borne by the landlords who can't supply housing at the new lower price
c. all consumer surplus is eliminated by the costs incurred through search activity
d. consumers who do find housing at the controlled rent gain

correct option is D. consumers who do find housing at the controlled rent gain

Explanation:

we know that effective rent ceiling lowers the market rate below equilibrium rent

this will  increasing the quantity demanded of housing and decreases quantity supplied of housing

so there will be shortage of these and those consumers who can find housing at lower rent gains in the form of an increase in consumer surplus

so correct option is D. consumers who do find housing at the controlled rent gain

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