A Manufacturer of Silk Inspects Each Bolt of Material at the End

A manufacturer of silk inspects each bolt of material at the end of the manufacturing process. When the process is in control, it averages 11 defects per bolt. If a 2- sigma control limit is used, what should be done if a bolt is found with 3 defects?

A) Management should investigate and exploit the common causes of variation present.
B) Do nothing; the process is in control.
C) Do nothing, even though the process is out of control.
D) Management should investigate and exploit the assignable causes of variation present.