AHSME 1962 Problem 22

The number $121_b$, written in the integral base $b$, is the square of an integer, for $\textbf{(A)}\ b = 10,\text{ only} \textbf{(B)}\ b = 10\text{ and }b = 5,\text{ only}$ $\textbf{(C)}\ 2\leq b\leq 10 \textbf{(D)}\ b > 2 \textbf{(E)}\ \text{no value of }b$