What feature distinguishes this passage as an introduction?

This device blocks an opening along the base/floor of stairs or other walking or working surfaces where materials or body parts might otherwise inadvertently fall through. it should be 4 inches high, with not more than ¼ inch clearance above the floor

In 250-300 words, explain how the theme of social justice is explored in the novel. {to kill a mockingbird}

Which passage is an example of rising action in edgar allan poe`s "the black cat