For the translation of "he revealed to me what happened in France", the correct answer was: Il m'a révélé ce qui s'était passait en France.

Hi Ann,

Il m'a revelé ce qui se passait en France. -- He told me what was happened in France.

This sentence is actually reported speech. Say, your friend Mike tells you what is happening right now in France. A week later you are talking with your colleague Marie and tell her what Mike told you. Then you would say it in reported speech. And in reported speech, tenses get used in a specific way. Whetever Mike told you in present tense, you need to report to Marie in imperfect tense. For example:

Anne tells Julie, "I am tired." Then, a week later, Julie tells her other friend Muriel that Julie told her she was tired. This is how you would say it in French:

Anne : "Je suis fatiguée" (This is direct speech).
Anne m'a dit qu'elle était fatiguée. (This is reported speech).

If you look closely, reported speech in English isn't that different:

Anne: "I am tired."
Anne told me that she was very tired.

I don't think, reported speech has been covered yet in the lessons.

-- Chris (not a native speaker).

Sorry, a typo in my previous post. It should read:

Il m'a revelé ce qui se passait en France. -- He told me what happened in France.

Actually it's the pluperfect, not the imperfect. 

he revealed to me what had happened in France...

il m'a révélé ce qui s'était passé en France…