Why is the S&P $500$ index so readily used by equity$-$indexed annuity manufacturers?

A$)$ The S&P $500$ includes industrial, utility, financial, and transportation issues and is market$-$weighted so that each stock impacts the index in proportion to that stock's importance in the market.

B$)$ The S&P $500$ is comprised of the largest $500$ U$.$S$.$ stocks or companies.

C$)$ The S&P $500$ reflects the short$-$term growth potential of equity$-$linked returns: equities that outperform fixed$-$interest vehicles and inflation.

D$)$ The S&P $500$ includes stocks from the NYSE, the ASE, Nasdaq, DAX, FTSE, and the Nikkei.