Which of the alternatives describes one of the Supervisory Authority’s responsibilities?

The correct option is the responsibility of the Supervisory Authority, the others are the responsibility of the processor.

GDPR Article 3 decrees:

This Regulation applies to the processing of personal data of data subjects who are in the Union by a controller or processor not established in the Union, where the processing activities are related to:

a)the offering of goods or services, irrespective of whether a payment of the data subject is required, to such data subjects in the Union; or;

b)the monitoring of their behaviour as far as their behaviour takes place within the Union.