[A]: Active transport results in solute move- ment against a concentration gradient.
[R]: Active co-transport of `Na^+ and K^+` is ener-gized by ATP.
A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false