French language Q&A Forum

Is there a lesson that explains this use of l/le? I see it a lot, but I don't fully understand when it is needed and when it isn't needed. 

which is the correct level?

Quelle est la différence?

Bonjour:)  Would you please review the kwiz answer I missed in the above lesson?  I did not find any of the possible choices for an answer to be particularly applicable.  The actual answer seemed like it was l'imparfait situation in the past so I did not choose that one.  I knew "built" was not a verb used in the choice but it seemed to imply the present tense to me.  Anyway, many thanks for some clarification on this question at your convenience I hope?  Merci.