Why does a returning boomerang curve back toward the thrower?

Answer: Spinning creates unequal lift

Spinning creates unequal lift ✓ — Correct! A returning boomerang has wing-shaped arms. As it spins, the arm moving forward through the air goes faster than the one moving backward, so it generates more lift. That unequal lift creates a torque that tilts the spin axis, and gyroscopic precession makes the flight path curve around and come back to the thrower.

Magnetic force attracts them — Wrong. There is no magnetism involved. A boomerang returns through aerodynamic forces: its spinning wing-shaped arms create unequal lift, which produces a torque and a curved flight path.

Shape makes them bounce — Wrong. A boomerang does not bounce off anything. It flies in a curved path because of gyroscopic precession caused by unequal lift on its spinning arms.