Other things remaining the same, and assuming that $\stackrel{}{x}$ is smaller than USL and larger than LSL$,$ if the standiard deviation $($d$)$ of the process decreases, process capability index $($Cpk$)$ of the process will

$1\mathrm{.}1.$ Stay the same

$2.$ II$.$ Will always increase

$3.$ III. Will always decrease

$4.$ IV$.$ Will sometimes increase

$"$

Either II or III

$1$

III

IV