Step 1: Word meaning.
The word "Concert" means a musical performance given in public, usually by several performers or an orchestra.
Step 2: Checking spelling variants.
(A) Concert: Correct spelling.
(B) Koncirt: Incorrect, uses wrong letters "K" and "i."
(C) Cauncert: Incorrect, extra "au" makes it wrong.
(D) Councert: Incorrect, "oun" is not part of the correct spelling.
Step 3: Conclusion.
Thus, the correct spelling is (A) Concert.