You need only make three options available
Generally speaking paragraph 2550.404c-1 requires that the plan " provides a participant or beneficiary an opportunity to choose, from a broad range of investment alternatives " ((b)(1)(ii)) and goes on to indicate ((b)(3)(i)(C)-1) that this can be accomplished with " At least three of the investment alternatives made available pursuant to the requirements of paragraph (b)(3)(i)(B) of this section, which constitute a broad range of investment alternatives ."
The requirements of (b)(3)(i)(B) are very specific and fairly lengthy. In attempt to be brief, three options will only suffice if they have materially different risk and return characteristics, are each alone diversified, and together allow the participant to " achieve a portfolio with aggregate risk and return characteristics at any point within the range normally appropriate for the participant or beneficiary ".
You can accomplish the requirements of 404(c) with just three options if you satisfy the specific portfolio construction characteristics enumerated by the DOL. This is not a simple task and requires portfolio science and investment management expertise. It should also be noted that the regulations indicate that an "option" might consist of a category of investments (like Domestic Large Cap Equity) with several investment alternatives available within that category and that more than three categories can be used to achieve the requirements for a properly constructed set of investment options.