Most 401 (k)s offer investment options such as mutual funds. Investment options in the mutual funds can be stocks or bonds or a combination of both. As we age, providing a layer of safety and security to our 401 (k) seems only prudent. As an option, your 401 (k) will also offer a stable money investment option. These options could include a money market account. The problem with money market accounts is the yield, a yield which may not keep up with inflation.