Final answer:
The most effective control in offsetting the weakness of the accounts receivable clerk approving credit memos and having access to cash is having the owner review credit memos after they are recorded.
Step-by-step explanation:
The most effective control in offsetting the weakness of the accounts receivable clerk approving credit memos and having access to cash would be option c - The owner reviews credit memos after they are recorded.
This control ensures that a higher-level authority, the owner, reviews and approves the credit memos to minimize the risk of fraudulent or inappropriate approval. Having the owner review the credit memos after they are recorded, it adds an additional layer of oversight and reduces the likelihood of unauthorized or unsupported credit memos.
Furthermore, having the owner involved in the review process increases accountability and promotes a separation of duties, which is an important internal control principle in preventing fraud. The other options listed also provide certain controls, but option c specifically addresses the weakness highlighted in the question.