Using the S & P500 Portfolio as a Proxy of the Market

Using the S & P500 portfolio as a proxy of the market portfolio

A) is appropriate because U.S.securities represent more than 60% of world equities.
B) is appropriate because most U.S.investors are primarily interested in U.S.securities.
C) is appropriate because most U.S.and non-U.S.investors are primarily interested in U.S.securities.
D) is inappropriate because U.S.securities make up less than 50% of world equities.
E) is inappropriate because the average U.S.investor has less than 20% of her portfolio in non-U.S.equities.