Aunque and sino not taught in Spanish Conjunctions lesson
When I went back to strengthen my skills in the Conjunctions lesson in Spanish, I was given the words "aunque" (translated as "though") and "sino" (translated as "but"). However, I didn't remember actually learning these words when I did the original course.
Lesson 2 of Conjunctions lists the following words: cuando, aunque, sino, mientras, and como. I clicked on "redo" and went through the lesson again, and sure enough, there were NO items with either "aunque" or "sino." This needs to be corrected so that these words are taught the first time around!
I had the same problem with "periodico" in another lesson. I love love love Duolingo and it's been great for learning Spanish, but the lessons need to be "proofread" for these sorts of omissions!
There are at least 3 sentences for each new word taught by Duolingo. Lessons usually teach 6 - 9 new words. In recent times, I have found new lessons sometimes taking as few as 7 exercises for completion. With this, it is possible that some words are not taught the first time one completes a lesson. Redoing a few times usually brings out all words. But sometimes, a word may make an appearance only during revision.