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.
In the short term, the voyages led to the destruction of the natives of the lands that Columbus found. Some of them were killed outright. Others were enslaved. Many died of diseases brought by the Europeans.
I believe the answer would be the second choice.
