Answer:
Barbara
Explanation:
The answer is "Barbara".
O’Malley, who was the owner in fee simple of Blackacre delivered a deed to Abel and the deed reads as "to Abel and his heirs." This means that O’Malley has has delivered the property of Blackacre in the hands of Abel and his heirs.
Blackacre is now a combine property of Abel and his heirs. They can together sell or transfer the property to some one else.
Abel then delivered a deed to Barbara of Blackacre. Thus the property now belongs to Barbara.
So now when Abel died, leaving his sole heir Callaway, the property still belongs to Barbara, and not to Callaway. Because Abel and Callaway who previously had ownership of Blackacre had delivered a deed to Barbara.
Thus Barbara owns Blackacre.