Which of the Following Explains the Primary Use of Levey-Jennings

Which of the following explains the primary use of Levey-Jennings charts?

A) Determination of the best fit line through a large set of data points
B) Generation of a standard curve from which information about a sample, such as concentration, can be determined
C) Identification of outliers, trends, and shifts in data that may indicate a malfunction or other problem
D) Maintenance of laboratory equipment in compliance with the International Sensitivity Index (ISI)