Question

Which of the following is a correctly written compound word?
1) Thirty one
2) Self-evident
3) Quickly-running
4) Spur of the moment-decision

It would be great if you could provide me with a answer and explanation. Thank You

Answer 1

# 2 is correctly written. Check this site for hyphenation rules.

http://owl.english.purdue.edu/handouts/grammar/g_hyphen.html

Answer 2

Thanks for the website info!!