SAT Question 9912e19f: Lines, Angles, and Triangles answer and explanation with Desmos solution

Choice B is correct. It's given that triangles $EFG$ and $JKL$ are congruent such that angle $E$ corresponds to angle $J$. Corresponding angles of congruent triangles are congruent, so angle $E$ and angle $J$ must be congruent. Therefore, if the measure of angle $E$ is $45^{\circ }$, then the measure of angle $J$ is also $45^{\circ }$.