Choice "D" is correct. The initiative to communicate with the predecessor auditor rests with the successor auditor. Note, however, that the successor auditor must first receive permission from the client.
Choice "b" is incorrect. The predecessor auditor should respond promptly and fully to reasonable inquiries. However, the predecessor is not responsible for initiating communications.
Choice "a" is incorrect. The prospective client should authorize the predecessor to respond fully to the successor's inquiries. However, the client is not responsible for initiating communications.
Choice "c" is incorrect. The prospective client should authorize the predecessor to respond fully to the successor's inquiries. However, the client is not responsible for initiating communications.