"Ĉar" vs "Pro"
Which is the right answer to "kial"? "Ĉar", "Pro", both, or another one? Is any difference between them?
I agree with amuzulo. Ĉar introduces a sub-clause that shows a cause, reason or motive. You could also say: ĉar = pro tio, ke. Pro is a preposition. It does indeed mean because of, on account of, for the sake of, due to. If you get a question that starts with kial, in most cases you should expect a sub-clause in the answer. e.g. Kial la vetero estas malvarma? La vetero malvarmas, ĉar la vento estas tre forta (or).....la vetero malvarmas pro la forta vento. I hope that this makes sense.
Ĉar is "because" (and introduces a subclause) and Pro is "because of".
Thanks for answering here as well... Facebook posts will be lost forever and perhaps in the future is possible to query the Duolingo forums or find answers here through google.
Since it is a company you should wait until the big data trend arrives here...