GDPR: What is meant by an "opening clause"? Tick the correct answer.

a$)$

it is a provision within the GDPR stating that the GDPR is applicable for controllers located in third countries even if they are not processing personal data of data subjects within the European Union.

b$)$

It exempts certain areas from the applicability of the GDPR$.$

c$)$

It enables member states to enact individual privacy laws within the scope of the respective opening clause.

d$)$

It is $-$ by itself $-$ a legal basis for processing, such as consent or the fulfilment of a contract