What sound signal alerts others that a boat is backing up?

How did the house of wisdom contribute to social developments during the golden age

What did palestinian leader mahmoud abbas promise after succeeding yasir arafat in 2004?

What does the country say concerning the status of free blacks living in the united states? a) they have the same rights as any other "free" people, and are full citizens. b) they have the same rights as any other "free" people, but are not properly citizens. c) they are citizens, but don't have the full rights granted to other citizens. d) they are not citizens, and have no right to petition the court.