Is certification to ISO $9001$:$2015$ an "upgrade" compared to ISO $9001$:$2008$ version?

Select one:

a$.$ No$,$ companies that are certified to ISO $9001$:$2008$ are on the same level.

b$.$ The $2008$ standard is much more restrictive, so only large companies are eligible.

c$.$ Yes, there is a big difference between this Standard and the previous one from $2008.$