A、She attended a training class. B、She learned it by herself. C、She learned it from a friend. D、She learned it by watching video

M: Good morning, Mrs. Dudley. I am a school paper reporter and I hear that you are very keen on shadowboxing. So I’d like to ask you a few questions.
W: Go ahead, please.
M: Firstly, I wonder if you could tell me something about how you learned shadowboxing.
W: (19)I attended a training class and was taught by a nice teacher. I had to watch closely my teacher’s precise and controlled movements. It was really difficult and stiff at first to control my movement.
M: Then how do you hold up afterwards?
W: Well,(20)practice is the most important of all, more important than a good teacher, comfortable learning environment and advanced learning device. After class, I spent a lot of time practicing. Although I came across some difficulties now and then, I was never disheartened. I know I was making progress every day. As time went on, I was more and more skilled in it.
M: Yeah, I can see that. Now you are doing wonderfully.
W: It’s so kind of you to say so. But I really take pains to do that.
M: I hope you won’t mind telling me how long you have been doing shadowboxing.
W: I have been doing it for six months. Almost three hours each day at the first two months.
M: How do you feel after you have done it for six months?
W: (21)I feel very well and it is really worth learning. And I will keep doing it.
M: OK, Mrs. Dudley, thank you. I think I will have an interesting story to tell in the coming report.
W: I am looking forward to reading your report.
19. How did the woman begin her shadowboxing learning?
20. What is critical to learn shadow boxing according to the woman?
21. What does the woman think of shadowboxing learning?