When the type I error is specified, which of these is correct expression for the UCL of the modified control charts?

• A. (UCL=USL- left(Z_ + frac{Z_ }{ sqrt{n}} right) sigma )
• B. (UCL=USL- left(Z_ - frac{Z_ }{ sqrt{n}} right) sigma )
• C. (UCL=USL+ left(Z_ + frac{Z_ }{ sqrt{n}} right) sigma )
• D. (UCL=USL+ left(Z_ - frac{Z_ }{ sqrt{n}} right) sigma )