听力原文：M: Hi, Helen, what do you think of our class in Children' s Literature？
W: It looks pretty good. Are you also majoring in Elementary Education？
M: Yes. I can use this to fulfill the requirement in my course.
W: Have you finished the first assignment yet？
M: Not yet. I just bought the books today. How about you？
W: I started this afternoon. It' s great fun reading those wonderful children stories by Doctor Seuss.
M: Doctor Seuss？ I don't remember seeing his name on the reading list.
W: His full name' s Theodore Seuss Geisel. You can find this name on the reading list. Doctor Seuss is his pen name.
M: I love reading those stories as a child. It' Il be interesting to read them now from a different point of view. I guess they'll give me a good idea of how children think.
W: Those stories are also great for classroom use.
M: How' s that？
W: Well, take a typical Doctor Seuss' book like The Cat in the Hat. It has controlled vocabulary of only two hundred words.
M: So that means the children get lots of practice using a small number of words over and over.
W: Exactly. hi fact The Cat in the Hat was written mainly to show how a controlled vocabulary reader could also , be interesting and fun.
M: Well, it sounds as though this course is also going to be interesting and fun. I think I'll get started on those readings tonight.
What is Helen' s major field of study？

A. Children' s Literature.
B. American Literature.
C. Medicine.
D. Elementary Education.