Step 1: Understanding the Concept
In $(1+x)^N$, the greatest coefficient is the middle one.
Step 2: Evaluation
Here index is $2n$ (even).
Step 3: Middle Term
The middle term coefficient for an even index $N$ is ${}^NC_{N/2}$.
Step 4: Conclusion
Greatest coefficient $= {}^{2n}C_{n}$.
Hence, the Answer is: (A)