Which sentence uses punctuation to set off the nonrestrictive (parenthetical) element correctly?

A. The concert will be held on Saturday (which is my favorite day of the week).
B. The concert will be held on Saturday (which my favorite day of the week).
C. The concert will be held on Saturday, which is my favorite day of the week.
D. The concert will be held on Saturday which is my favorite day of the week.