Which of the following is NOT true in regard to calculating physical volume?

Which of the following is NOT true in regard to calculating physical volume?
 
  A) The basic formula for calculating volume is lengthwidthdepth.
  B) If the item is not a perfect rectangle, take the average width and length. For example, if the object is 6 inches at its widest point and 2 inches at its narrowest point, use 4 inches for the width.
  C) If you are wrapping the item in bubble wrap, take your measurements before it is wrapped.
  D) If you take your measurements in inches, your final calculation will be in cubic inches. If you take them in centimeters, your final calculation will be in cubic centimeters, and so on.