Investment Policy Statement for Conservative Growth Strategy

John and Mary Smith are affluent clients seeking guidance on their investment strategy for retirement. After a thorough risk tolerance evaluation and understanding their financial goals, you draft an Investment Policy Statement (IPS) tailored to their needs. The IPS is comprehensive, outlining investment objectives and constraints. One of the key aspects of the IPS involves specifying the preferred investment vehicles and underlying strategies.

Given the Smiths' desire for capital preservation, a medium growth rate, and a willingness to accept some volatility, which choice should be included in the IPS as the primary investment approach that aligns with their profile?