In this task, you're given an open-domain question. Your task is to provide an answer to the given question. There is only one unique answer for each question. Your answer should be short, and refer to an entity, date, number, etc. Do not put your answer in the context of a sentence.

The medical term for a superficial loss of skin as would occur by scratching is?
abrasion

When did leningrad changed back to st petersburg?
6 September 1991

Where does the blood in the right atrium come from?

coronary sinus