Which words means "to study a specific subject"?

Which word means, "to prove my giving evidence"?

Which word means, "to be particular or precise"?

Which word means, "a promise or agreement to do or not to do something"?

Which word means, "to put together"?

Which word means, "to complain about something in a quiet voice"?

Which word means, "to determine the answer"?

Which word means, "something that is high quality and fancy"?

Which word means, "a special benefit enjoyed only under special circumstances"?