The correct option is D 2nCn.xn
Middle term =N2+1
=2n2+1
=(n+1)th term
Now consider the following,
Tr+1=nCran−rbr...(i)
Where T represents the term
Here the middle term is the (n+1)th term
Hence r+1=n+1
∴r=n
Substituting in (i), we get 2nCn12n−nxn
=2nCnxn
Hence answer is D