Select the best answer for this statement: An inhomogeneity in a variable's record might be caused by ... Question 18Select one: a. Periodic instrument failure b. Changes in the environment where the measurements were taken c. A change in the person taking the measurements d. A change in the time of day that measurements were taken e. A change in the instruments recording the variable f. A bias in the instruments recording the variable g. All of the above, except a h. a and e only i. b, c, d, and e only