1958 AHSME Problem 49

In the expansion of (a + b)^n there are n + 1 dissimilar terms. The number of dissimilar terms in the expansion of (a + b + c)^{10} is:

\textbf{(A)}\ 11\qquad \textbf{(B)}\ 33\qquad \textbf{(C)}\ 55\qquad \textbf{(D)}\ 66\qquad \textbf{(E)}\ 132

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.