Tracts sold under this part may only be conveyed to:

(a) A citizen of the United States 18 years of age or over;

(b) A corporation subject to the laws of any State or of the United States;

(c) A State, State instrumentality or political subdivision authorized to hold property; and

(d) An entity legally capable of conveying and holding lands or interests therein under the laws of the State within which the lands to be conveyed are located. Where applicable, the entity shall also meet the requirements of paragraphs (a) and (b) of this section.