It really depends on your type of data, if it's sensitive data or not. And it also depends on what type of backup (Incremental, Decremental, etc.). But you should aim to backup at least once a week, and also do a backup of your original backup.
I believe it is C, I'm so sorry if im incorrect.
HyperText Markup Language
Answer:
update
Explanation:
a table of contents does not update itself automatically.