Jackson wants to know how an insurance company can offer interest credits in an equity$-$indexed annuity based off of stock market returns when it does not invest directly into the stock market like stock mutual funds do$.$ The way in which the company issuing the annuity is able to do this is by employing which one of the following investment strategies?

A$)$ By taking the funds not needed to support the contractual guarantees and buying Inflation Protected Securities $($IPS$)$

B$)$ By taking the funds not needed to support the contractual guarantees and speculating in the futures market

C$)$ By taking the funds not needed to support the contractual guarantees and purchasing guaranteed stock mutual funds available only to institutional investors like insurance companies

D$)$ By taking the funds not needed to support the contractual guarantees and purchasing call options on a particular index