The first one answer is the correct answer
Six million Jews<span>
Six million Jews died in the Holocaust. Jewish communities across Europe were shattered. Many of those who survived were determined to leave Europe and start new lives in Israel or the United States. Most of these Jews were killed by the Germans because Hitler believed the Jews were the cause of Germany's economic problems. He employed mass killings and created concentration camps in which they would be killed.</span>
No they aren't proper to use in writing class they are considered slang. It would show your teacher that your not interested in sounding educated and proper.
Hope this helps!
