Which of the Following Statements Is Correct Regarding Control Charts

Multiple Choice

Which of the following statements is correct regarding control charts?
I. Specification limits are the same as control limits
II. If there is no assignable cause of variation the process is in control
III. A shift in the or average will show up on the X portion of the X and R chart

A) I and II are true
B) I and III are true
C) II and III are true
D) all the above are true
E) none of the above is true