SAT Question 992f4e93: Lines, Angles, and Triangles answer and explanation with Desmos solution

Choice A is incorrect and likely results from thinking the angle with measure $a^{\circ }$ is the complement of the angle with measure $64^{\circ }$.

Choice B is incorrect and likely results from thinking the angle with measure $a^{\circ }$ is congruent to the angle with measure $64^{\circ }$.

Choice D is incorrect and likely results from a conceptual or computational error.