TOEFL Listening: ETS-TOEFL听力机经 - X2X5L645ATQXQ4L0P$

What was responsible for the successful movement to the platinum-gold rod nanoengine? A. Hydrogen peroxide destroyed bacteria cells blocking the engine's paths. B. The combination of two chemical reactions created a proton imbalance. C. Interactions between the platinum and gold cost the rod to spin quickly. D. The magnetic field that surrounded the engine was destabilized.