Based on the clue 'adding this vitamin to milk has basically eliminat...', what is the answer?

Based on the clue 'adding these charged particles to the air is suppo...', what is the answer? Based on the clue 'adding this letter to heritage gives you a nice se...', what is the answer? Based on the clue 'adding this letter to orpheus makes him a pretty d...', what is the answer? Based on the clue 'adding this mineral to toothpaste mouthwashed hel...', what is the answer? Based on the clue 'adding to a list that includes the pyramids andre ...', what is the answer? Based on the clue 'adding up the denominations of circulating bills w...', what is the answer? Based on the clue 'addis ababa is the capital largest city of this a...', what is the answer? What is referred to by 'addis ababa'?