Choice "C" is correct. The auditor would confirm the number of shares held by an independent custodian to establish the existence and ownership of a long-term investment in publicly traded securities.
Choice "d" is incorrect. The investee company may not have timely information regarding the ownership of its stock.
Choice "a" is incorrect. Inspection of the audited financial statements of the investee company does not provide evidence about ownership of the securities.
Choice "b" is incorrect. Determination that the investment is carried at the proper market value provides assurance about valuation and about appropriate presentation and disclosure in the financial statements.