To identify the correctly spelled word, we must examine each option for standard spelling according to English usage.
Option A: "rejuvanation"
The correct spelling is "rejuvenation" — with an "e" after the "j".
"Rejuvanation" is a common misspelling.
Option B: "excarsion"
This is an incorrect spelling. The correct word is "excursion", meaning a short journey or trip.
Option C: "abundance"
This is the correct spelling. It means a large quantity of something.
Option D: "advantagious"
The correct spelling is "advantageous" — it ends with "eous", not "ious".
Hence, only Option C is spelled correctly.