I have yet to hear a Vietnamese individual say "Cuộc sống là ngắn quá." I have heard individuals say, "Cuộc sống ngắn quá" (which was considered incorrect). I don't understand why the word choices reveal the former sentence as the correct answer.
Thanks for the observation; I had the same question.
I agree as well. Almost always quá as modifier comes after the adjective in the way I've heard it used.