Chapter?2 The?Chemical?Context?of?Life Multiple-Choice?Questions 1) About?25?of?the?92?natural?elements?are?known?to?be?essential?to?life.?Which?four?of?these?25?elements?make?up approximately?96%?of?living?matter? A) carbon,?sodium,?chlorine,?nitrogen B) carbon,?sulfur,?phosphorus,?hydrogen C) oxygen,?hydrogen,?calcium,?sodium D) carbon,?hydrogen,?nitrogen,?oxygen E) carbon,?oxygen,?sulfur,?calcium Answer: D Topic: Concept?2.1 Skill: Knowledge/Comprehension 2) Trace?elements?are?those?required?by?an?organism?in?only?minute?quantities.?Which?of?the?following?is?a?trace element?that?is?required?by?humans?and?other?vertebrates? A) nitrogen B) calcium C) iodine D) sodium E) phosphorus Answer: C Topic: Concept?2.1 Skill: Knowledge/Comprehension