A、She feels unhappy working in male-dominated fields. B、She is fed up with the issue of gender discrimination. C、She is not good

(20)I don’t ever want to talk about being a woman scientist again. There was a time in my life when people asked constantly about what it’s like to work in a field dominated by men. I was never good at telling those stories because truthfully I never found them interesting. What I do find interesting is the origin of the universe and the shape of space-time.
     (21)At 19, when 1 began studying astrophysics, it did not bother me in the least to be the only woman in the classroom. But while earning my Ph.D. at MIT and then as a post-doctor doing space research, the issue started to bother me. Sometimes, when I was pushed into an argument on left brain versus right brain, I would instantly fight fiercely on my behalf and all womankind.
    Then one day a few years ago, out of my mouth came a sentence that would eventually become my reply to all provocations: I don’t talk about that anymore. It took me 10 years to realize that I didn’t want to deal with gender issues.
    Today I research and teach at Barnard, a women’s college in New York City.(22)The 45 students in my class were all women. I know some of my students worry how they manage their scientific research and a desire for children. And I give them a physics professor heavily pregnant doing physics experiments. In turn they give me the image of 45 women driven by a love of science. And that’s a sight worth talking about.
Questions 20 to 22 are based on the passage you have just heard.
20. Why doesn’t the author want to talk about being a woman scientist again?
21. When did the issue of being the only woman in her field start to puzzle her?
22. What does the image the author presents to her students suggest?