Question 664·Easy·Math

Since $O$ is the center, $\angle AOB$ is a central angle, an angle with its vertex at the center. A full turn is $360^\circ$, so the given $135^\circ$ covers this fraction of the circle:

Type $\frac{135}{360}$ in Desmos. It shows $0.375$; click the fraction button beside it to see $\frac{3}{8}$. Because $135^\circ$ is less than a half turn, this fraction belongs to the minor arc, the shorter path from $A$ to $B$.

The given $32$ is the circumference, the distance all the way around the circle. The arc takes the same fraction of the circumference as its central angle takes of a full turn. So write: $\text{arc length}=\frac{3}{8}(32)$. The $135^\circ$ is an angle, not a length.

Type $\frac{3}{8}\cdot32$ in Desmos; it shows $12$. So the length of minor arc $AB$ is $12$. Choice B.