看了一些外国学生的回答,我觉得以下这个比较有道理：
Struggles are experiences.The songs describe experiences,especially the experiences in which black women struggled to adjust to urban life in the northern U.S.The songs describe experiences,especially the struggles of black women to adjust....The sentence is stating what types of experiences (i.e.,struggles) southern Black migrants are especially experiencing.
In B,"struggled at adjusting" should be "struggled to adjust." "How Black women struggled to adjust" is not an experience,so you can't say,"Bessie Smith's songs describe the experiences,...especially how they struggled." The struggle itself is an experience,but how they struggled is just an attribute (description) of the struggle.