A
Christine and her friend Zelda were going away to college and had quite a few personal belongings to transport. Christine's father offered to drive them in his van, but when the van was loaded they discovered there was only room for two people, so Christine asked her boyfriend Harry to drive her in his car while Christine's father and Zelda rode in the van. About halfway to the college, while the van and Harry's car were driving down the freeway, the van in front, the van suddenly swerved out of control and ran off the highway, ending up on its side in the center divider. When Harry stopped his car and Christine ran to the van, she discovered to her horror that her father was dead. Zelda appeared to be injured, but not severely. Because her father previously had heart trouble, Christine assumed that he had had a heart attack while driving, although a later investigation would reveal that the accident was caused solely by a defect in the steering mechanism of the van. Filled with remorse, Christine told Zelda, "I'm so sorry about this. I'll make good any losses you suffer because of this accident." Later, when Christine learned that Zelda was going to seek treatment from Dr. Winston, she wrote the doctor a letter stating that she would be responsible for all of Zelda's medical expenses; Dr. Winston received the letter the next day. Assume for purposes of this question only that, after treating Zelda for her injuries until she recovered, Dr. Winston sent Christine a bill for services rendered. When Christine refused to pay, Dr. Winston brought an action to recover the amount of her bill. Who will prevail?
A. Dr. Winston, because she gave medical treatment to Zelda after receiving Christine's letter. 
B. Dr. Winston, because Christine's promise to pay Zelda's medical expenses was in writing.
C. Christine, because there was no consideration for her promise to Dr. Winston.
D. Christine, because she derived no benefit from the medical services rendered to Zelda.