Which motion of particles across a membrane requires energy?. A) from high concentration to low concentration. B) from low concentration to high concentration. C) with no concentration gradient. D) through dynamic equilibrium

B) from low concentration to high. This is because, naturally, particles will move from high to low concentration areas. In order to move from low to high, the particles sort of have to be forced, which requires energy

The correct answer among the choices listed is option B. The motion of particles from low concentration to high concentration across a membrane requires energy. This is because usually the particles flow from high to low and in order to flow the opposite energy should be supplied.