Nida is asked by a client to identify a security that he has heard a co-worker discuss as part of her portfolio. The security is described as allowing an easy and low-risk way to invest in mortgages, without having to own mortgages directly. What security is Nidas client's co-worker likely holding?

		Securitized Debt.
		First Mortgage Bond.
		Real Estate Investment Trust (REIT)
		Mortgage-backed Security (MBS)