Digital SAT Reading and Writing Practice Question #541

Researchers theorize that the European robin navigates using a quantum phenomenon known as the radical pair mechanism. Cryptochrome proteins in the bird's retina absorb blue light, creating pairs of entangled electrons whose spin states are exquisitely sensitive to Earth's magnetic field. This sensitivity dictates the chemical products formed in the retina, effectively allowing the bird to "see" magnetic lines. However, experiments demonstrate that if the robins are exposed exclusively to red light, their orienting abilities vanish entirely. Furthermore, when oscillating radio frequencies—which actively disrupt electron spins without affecting light absorption—are introduced in a blue-light environment, the birds are equally disoriented. Together, these findings suggest that ______