How did Sri Lanka’s location allow it to prosper for many centuries?

Hewo!

It would be because of it's location on an very important see route between Africa and Asia.

FunFact - Sri Lanka looks like a landmass in the shape of Potato.

Hope it helps!!!

The main function of the Department of Homeland Security is to protect the United States.

Explanation:

The United States Department of Homeland Security (DHS) is a US government department whose responsibility it is to protect the US territory against terrorist attacks and to act in the event of natural disasters.

While the Department of Defense is in charge of military action abroad, the Department of Homeland Security works in the civilian sphere to protect the US territory inside and outside its borders. Its purpose is to prepare, prevent and respond to domestic emergencies, particularly terrorism.  

With more than 200,000 employees, DHS is the third largest federal department of the US government, behind only the Department of Defense and Department of Veterans Affairs. The internal security policy is coordinated by the White House by the Homeland Security Council. Other agencies with significant internal security responsibilities include the Department of Health and Human Services, the Department of Justice, and the Department of Energy.