Some people referred to Prohibition as a "noble experiment" because it

led to people home-brewing alcohol.

was never expected to improve morals.

tried to force people to improve their morals.

had the support of upstanding citizens.

The best answer is the following one;

tried to force people to improve their morals.

The prohibition tried to make people stop drinking alcohol, which can be seen as "noble". People did not decide it themselves but it was forced on them, so it is justified to say that the law during the Prohibition time tried to force people to improve their morals.

Option C. tried to force people to improve their morals.