Answer
Choice B
Work Step by Step
The probability of getting a $2$ when a standard number cube is rolled is $\dfrac{1}{6}.$ Also, the probability of getting a $3$ when a standard number cube is rolled is $\dfrac{1}{6}.$ Adding these probabilities, then the probability of getting a $2$ or a $3$ is
\begin{align*}\require{cancel}
&
\dfrac{1}{6}+\dfrac{1}{6}
\\&=
\dfrac{2}{6}
\\&=
\dfrac{\cancel2^1}{\cancel6^3}
&\text{(divide by $2$)}
\\&=
\dfrac{1}{3}
.\end{align*}
Hence, Choice B.