"I thank you."
As stated by Olimo below 'благодарю' is bookish and I have been informed by Russian speakers that it is hardly ever used and 'спасибо' is the universal form of thank you, so why is duolingo teaching it?
It wasn't Duolingo, but a different language course, that was teaching "morn" as "hello" in Norwegian, which is something only 80+ year olds say, and is not even bookish haha
When do you use "спасибо" vs. "благодарю"? Is one just more formal?
"Спасибо" is the most universal word which is fine to say both to a child or a president :-) "Благодарю" is sort of bookish, it is never used informally.
This does not sound natural. You can say "Я вас благодарю", but this also is not common in normal speech. Looks like a line from a song or poem.
Why is the p at the end of благодарю not being pronounced like an "r", as usual? Or am i hearing it wrong?
With a capital B its the polite version of the 2d person singular, like the "vous" in French or "usted" in spanish
I like bookish stuff sometimes, boosts some memory and cultural history of langages.