Again- without an articel it only works in plural: " Students like to sing National Anthems." All over the world.If one wants to put the sentence in the singular it wants an articel :"Pupils like to sing the National Anthem." All pupils the same one. It still is pretty much a turn off to try to rember all the mistakes in English-mainly the random use of articles and seeing that you neither get hints for the wanted use nor getting anything fixed...

This is by far the most frustrating part-course I've encountered on Duolingo. And the program has me practicing it over and over again, since "I cannot seem to get it right" (which is impossible on the first try, since so many answers are illogical and don't allow for any variation)

Agreed it causes a lot of frustration