The process capability measures $C_p$ and $C_{pk}$ differ because:

Select one:

a$.$ They do not differ: both are identical.

b$.$ Both only one ensures the process mean is centered within the limits and $C_p$ values for a given process will always be greater than or equal to $C_{pk}$ values are correct.

c$.C_p$ values for a given process will always be greater than or equal to $C_{pk}$ values.

d$.$ only one ensures the process mean is centered within the limits$.$

e$.$ C p values above $1$ indicate a capable process, while $C_{pk}$ values above $2$ indicate a capable process.