(A) In general Amounts contributed under paragraph (4)(B)(i) shall be invested only in the class of assets or funds described in subparagraph (B) unless the employee elects a class of assets or funds described in subparagraph (C), (D), or (E). (B) Target date or lifecycle option The class of assets or funds described in this subparagraph is the class of assets or funds that constitutes a qualified default investment alternative under section 2550.404c–5(e)(4)(i) of title 29, Code of Federal Regulations. (C) Principal preservation The class of assets or funds described in this subparagraph is the class of assets or funds that is designed to protect the principal of the individual on an ongoing basis, including passbook savings, certificates of deposit, insurance contracts, mutual funds, United States savings bonds (which may be indexed for inflation), and similar assets specified in regulations. (D) Guaranteed lifetime income option or equivalent The class of assets or funds described in this subparagraph is the class of assets or funds that is designed to provide an employee with the right to elect to receive distributions as a defined level of income annually (or more frequently) for at least the remainder of the life of the employee or the joint lives of the employee and the employee’s designated beneficiary. (E) Other Any other class of assets or funds determined by the Secretary to be a qualified investment for purposes of this section. (7) Qualifying retirement bond For purposes of this section— (A) In general The term qualifying retirement bond means a bond issued under chapter 31 of title 31, United States Code, which by its terms, or by regulations prescribed by the Secretary under such chapter— (i) provides for interest to be credited at rates that take into account the expected duration of the funds invested in such bonds and at rates determined or adjusted in a manner and with sufficient frequency to provide substantial protection from inflation, (ii) is not transferable, and (iii) is designed for