Which amendment gave the government the power to impose an income tax?

The 16th Amendment is the correct answer because it specifically grants Congress the authority to levy an income tax without apportioning it among the states based on their population. Ratified in 1913, this amendment was a significant change in the power of the federal government, allowing it to impose a direct tax on individual earnings. Prior to this amendment, the government struggled to collect income tax effectively due to legal challenges regarding apportionment requirements. The 16th Amendment eliminated this barrier, making it possible for the government to raise revenue more efficiently through taxation on income.

The other amendments listed do not pertain to income tax; the 14th Amendment primarily addresses citizenship rights and equal protection under the law; the 18th Amendment instituted Prohibition, banning the sale of alcoholic beverages; and the 23rd Amendment granted residents of Washington D.C. the right to vote in presidential elections. Thus, the 16th Amendment's specific mention of income tax makes it the correct choice.