A Married Couple Is Unable to Conceive on Their Own

A married couple is unable to conceive on their own. The wife's younger single sister freely volunteers to donate a viable egg to the couple. What difficulty might Callahan have with this seemingly altruistic arrangement?

A) This self-sacrifice is being directed to fulfill the desires of the adult parents, not of the child who will be born.
B) A member of the extended family should not feel obligated to fill the role nature has designated for a biological parent.
C) The younger sister is not married; therefore, this violates the moral principle that only heterosexual married couples should conceive a child.
D) No financial responsibility is being taken for the inevitable discomfort from invasive procedures or powerful drugs the donor will need to receive.