Based on the clue 'atrial fibrillation may reduce the efficiency of t...', what is the answer?

Based on the clue 'atoms of this lightest element make up about 90 of...', what is the answer? Based on the clue 'atorvastatin is the generic name of this cholester...', what is the answer? What is referred to by 'atotc by charles dickens'? What is referred to by 'atph by cormac mccarthy'? What is referred to by 'att formerly sbc center'? Based on the clue 'att says more collect calls are made on this holid...', what is the answer? Based on the clue 'attach a pencil to a string pin the other end of t...', what is the answer? Based on the clue 'attach the letters one to a land run by a wizard ...', what is the answer?