(D) $\frac{(n+1)^n}{n!}$
Here $C_p=$$\binom{n}{p}$
Then,$\frac{C_p}{C_{p+1}}=\frac{p+1}{n-p}$
Then,$1+\frac{C_p}{C_{p+1}}=\frac{n+1}{n-p}$
For p=0 $=>$ $1+\frac{C_0}{C_{1}}=\frac{n+1}{n}$
For p=1 $=>$ $1+\frac{C_1}{C_{2}}=\frac{n+1}{n-1}$
and so on..
Thus if we multiply all the terms we get $\frac{(n+1)^n}{n!}$