What was the purpose of the eighteenth amendment? a. to improve the economy b. to repeal the poll tax c. to stop people from going to saloons d. to prohibition the manufacture of alcohol?

The correct answer here is D.
The 18th Amendment was ratified in year 1920 and effectively started what is known the Prohibition Era in the United States history. The 18th Amendment effectively banned the manufacturing, selling, transportation and the use of alcohol for the general public with the exception of use of alcohol in medical and religious purposes. The amendment was later repealed by the 21st Amendment in 1933.