Multiple choice questions
Being someone who wants to learn, i hate that I've noticed this. I can get virually every single multiple choice question without even trying to figure out the meaning of the words or know French.
You simply find the "two words/things" that are changed. The option that has one thing in common with each of the other two is the answer.
Also, if "they" is the subject, then there will almost always be two answers with "ils" and "elles"
Again, i hate that I've noticed this and I try to still learn anyway, but it's an annoying thing that makes it too easy I think. The programming probably just selects two words and changes them for the other two options. I feel they could mix it up more.
But I still really appreciate Duolingo.