In the context of a second-party audit, match the activity with the party responsible for...

Here is the correct matching of the activities with the responsible parties in the context of a second-party audit:

Define the audit scope: Customer

Develop the audit plan: Audit team leader

Respond to the audit findings: External provider

Conduct the audit: Audit team

This reflects the typical division of responsibilities in a second-party audit, where the customer (the party commissioning the audit) sets the scope, the audit team leader manages the planning, the external provider responds to findings, and the audit team carries out the audit.