As explained in the above thread, the conclusion of the argument is: "it should not be assumed that the profit motive is at fault."
Why? "It is unrealistic to expect investors to take risks with their property unless they get some benefit in return." We know that private investors will provide housing as long as the market permits them to make a profit.
Answer choice (D) is incorrect because the phrase "to the extent that homelessness arises from a lack of available housing" is not the conclusion, as identified above. Rather, it is a restriction placed on the argument so that we narrow our focus on homelessness arising out of a lack of available houses.
Hope that clears things up! Please let us know if you have any other questions.
