What is the appropriate financial statement disclosure for Company A after acquiring all shares of Company B?

The appropriate financial statement disclosure for Company A after acquiring all shares of Company B is to report the nature of and reason for the change in disclosure notes. This is crucial because acquisitions often significantly impact a company's financial position and performance, necessitating transparency to stakeholders.

When a company acquires another, it must evaluate and disclose how this acquisition affects financial reporting. By providing details about the nature of the acquisition—such as the rationale behind it, strategic goals, or expected synergies—Company A can help users of the financial statements understand the implications of this change. It sets the foundation for future disclosures and provides context for the company's operational and strategic direction.

In terms of the other options, while repeating acquisition disclosures for subsequent periods may be relevant, it is not the initial response required immediately after an acquisition. Disclosing only the financial position prior to acquisition fails to provide stakeholders with the necessary insights into how the acquisition alters the company’s financial landscape. Including an explanation in the management discussion and analysis can be helpful but is typically a secondary method of disclosure, meant to supplement primary financial statement notes following an acquisition. Thus, the most comprehensive initial approach is to clearly outline the nature and reasoning behind the change in disclosures stemming from the acquisition.