It's a hyperbole. Hyperbolas are meant to create a strong impression of something, but not to be taken literally.
The subject is sponge because that is what is the main point of the sentence is.
Sedative is to anesthesiologist as capital is to a "D.corporation". This is primarily because sedatives are used by the former to achieve their goals and capital is used by the latter.
The main idea of "Ain’t I a Woman" is to portray <span>the experience of an African American woman.
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