elements， hydrogen and helium. Heavier elements，

　　such as carbon， form only in nuclear reactions in

　　stars and are dispersed when the stars explode. A

　　recently discovered gas cloud contained carbon

　　several billion years ago， when the universe was

　　no more than two billion years old.

　　If the statements above are true， which of the

　　following must， on the basis of them， also be true？

　　（A）The earliest stars contained only hydrogen.

　　（B）Some stars were formed before the universe was

　　two billion years old.

　　（C）The carbon in the gas cloud later formed part of

　　some stars.

　　（D）No stars identified to date are as old as the gas

　　cloud.

　　（E）The gas cloud also contained hydrogen and

　　helium.

　　12.Sleep deprivation is a known cause of workplace

　　error， and many physicians frequently go without

　　sleep for periods of 24 hours or more. However， few

　　of these physicians have， in the course of a routine

　　examination by a peer， been diagnosed with sleep

　　deprivation.So there is little cause for concern that

　　habitual sleep deprivation will cause widespread

　　physician error.

　　The answer to which of the following questions

　　would be most helpful in evaluating the argument？

　　（A）Do physicians who have been diagnosed with

　　sleep disorders also show signs of other ills not

　　related to sleep deprivation？

　　（B）Is the ability to recognize the symptoms of sleep

　　deprivation in others significantly impaired by

　　habitual sleep deprivation？

　　（C）Do factors other than habitual sleep deprivation

　　ever lead to errors in the workplace on the part

　　of physicians？

　　（D）Of people who have recently been treated by

　　physicians， what percentage believe that many

　　physicians have occasionally suffered from sleep

　　deprivation？

　　（E）Is the incidence of sleep deprivation higher

　　among physicians than it is among other health

　　care workers？