According to Walter Shewhart: a) chance causes should be eliminated whenever possible
b) assignable causes could be ignored if they did not cause too much variation
c) the mean, uppercontrollimit, lower controllimit and warning lines that are two sigma from the mean are indicated by horizontal lines in the control chart
d) chance causes could be fixed
e) a control chart has time on the top axis and a plot of sample measurements

c) the mean, upper control limit, lower control limit and warning lines that are two sigma from the mean are indicated by horizontal lines in the control chart.

Explanation:

Walter Shewhart is regarded as an important personality in the history of quality management. He asserted that the behavior of real processes had the tendency to change as time changed and it was not the behaviur of theoretical random distributions.

Walter Shewhart posited that causes of variation could be divided into two which are chance cause and assignable cause. He maintained that chance causes could be ignored if they did not cause too much variation, and any attempt to eliminate them usually made the problem worse. He however posited that it was possible to fix assignable causes.

Walter Shewhart invented control chart in order to differentiate between variations caused by random events and trends that indicated assignable causes. There is time and a plot of sample measurements on the bottom axis of a control chart. The mean, upper control limit, lower control limit, and warning lines that are two sigma from the mean are indicated by horizontal lines.

Based on the above explanatio, the correct option is c) the mean, upper control limit, lower control limit and warning lines that are two sigma from the mean are indicated by horizontal lines in the control chart.