Active and passive transport of solutes across a membrane typically differ in which of the following ways? A] Active transport is usually against the concentration gradient of the solute, whereas passive transport is always down the concentration gradient of the solute.
B] Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy.
C] Active transport always requires the use of transport proteins, but passive transport can sometimes be accomplished without a protein.
D] The first and second choices are correct.
E] The first, second, and third choices are all correct.