Translation:The welfare is important to the citizens of the country.
Certain variants of English use it, usually as an abbreviation of "the welfare system". Cf. http://www.metrolyrics.com/when-the-welfare-turns-its-back-on-you-lyrics-albert-collins.html for an example.
Ah, it's Sonny Thompson, so I would guess that this is an archaic expression in Black American English. While he was born in Mississippi, Mr Thompson was a Chicago musician, and I can certainly tell you that one does not hear "the welfare" in the Chicago dialect of Black American English of the last couple of decades.
Duolingo uses whatever version of English the volunteers who put together the particular course speak. The Irish course, for instance uses Irish English and the Hindi course Indian English. I would say that, over all the courses, American English seems to be the most common. I assume the same is true of other working languages, so for instance, the Catalan course is based on the Spanish of Spain but the Guaraní course on that of the Southern Cone of South Ametica.
"Welfare is important..." We wouldn't say the welfare in English. Why hasn't this been changed after five years? We would say, "The welfare of the citizens is important in the country." That would refer to the general well-being of the citizens, but when we talk about welfare as government assistance, we don't use "the". Please trust us English speakers, Duolingo. We wouldn't force you to say something incorrect in Danish just to make us happy.