Which of the following statements is always true for any vectors a=axi^+ayj^+azk^ and b=bxi^+byj^+bzk^?
a) The z-component of a−b equals bz−az.
b) The y-component of a−b equals ay−by.
c) ∣a+b∣=∣a∣+∣b∣.
d) The x-component of a−b equals ax+bx.