After the narrator's "revelation," the tone of telephone conversation" becomes

If your options are A. gloomy, B. depressed, C. strained, D. teasing, I would say the correct answer is D. teasing. Prior to the revelation moment, the speaker is on the verge of depression, embarrassed by the fact that her Africanness is actually an issue. But then, she suddenly transcends this feeling and starts teasing the woman.