"Did you read today's newspaper ?"
AFAIK it is a limitation of the Duolingo platform which doesn't allow multiple different pronunciations for one word. In some circumstances 了 is pronounced "liǎo", though the far more common pronunciation is "le." So until this problem with Duolingo is fixed, the pronunciation will be wrong in at least some exercises.
This is hardly the only Chinese word affected. And, of course, the correct pronunciation in this sentence is "le."