The term “surviving divorced mother” means a woman divorced from an individual who has died, but only if (A) she is the mother of his son or daughter, (B) she legally adopted his son or daughter while she was married to him and while such son or daughter was under the age of 18, (C) he legally adopted her son or daughter while she was married to him and while such son or daughter was under the age of 18, or (D) she was married to him at the time both of them legally adopted a child under the age of 18.