Answer: a. Low initial credibility
Explanation:
Credibility is the perception of a speeker's attitude and competence,it shows the level of trust which the audience has of the speaker.
Following the scenero,the landlord who is coming to defend or give explanation to an anomaly, generally he will have a low initial credibility as the audience has an initial negative perception of him for failing to return security deposit at the end of a lease.
So the extent the audience will believe him will be low at the initial until he gives a good account of what has gone wrong.