Il y a des toiles d'arraignées partout. Tu ___as vue (Did you see them?)

Bonsoir Ann, Please repost to this with the lesson and that you are referencing. I do remember that question; however, not the specific lesson at hand. Merci,

The lesson they referred me to was the one explaining the use of articles le, la, les. No mention of the difference of when to use en... I always thought des was replaced by en.

Bonjour Ann, You are correct, «en» usually replaces a phrase beginning with «de»; however, what I have discovered using this application is this: when the lesson is about a specific topic, in this case le, la, les use, then anything other than the subject matter will be marked as incorrect. By like measure, then lesson that discusses the use of «en», then the same question would have been marked as correct. While I like this site and it's application, I find this type of thing as but one of the drawbacks in the use of computers for educational purposes, i.e. programs are unable to differentiate correct responses given under a different lesson heading. I hope this helps you. Bonne chance,

Please, do not misunderstand what I am trying to say above, I like Progress Lawless French very much and think that they do an excellent job at presenting the lessons. Because computers are «programmed» responses, a machine lacks the ability to make an educated judgement in differentiating correctness.

I wondered if the english of "did you see them" was a clue I should have caught? If it had said "did you see SOME would that have signaled how I should have answered?

I agree with your observation. SOME would have been a clue, vs the use of THEM.