根据下列内容，回答181-185题。
Modem scientists divide the process of dying into two stages--clinical or temporary death andbiological death. Clinical death occurs when the vital organs, such as the heart or lungs, haveceased to function, but have not suffered permanent damage. The organism can still be revived.
Biological death occurs when changes in the organism lead to the disintegration of vital ceils andtissues. Death is then irreversible and final.
Scientists have been seeking a way to prolong the period of clinical death so that the organismcan be revived before biological death occurs. The best method developed so far involves cooling ofthe organism, combined with narcotic sleep. By slowing down the body's metabolism, cooling de-lays the processes leading to biological death.
To illustrate how this works, scientists performed an experiment on a six-year-old femalemonkey called Keta. The scientists put Keta to sleep with a narcotic. Then they surrounded herbody with ice-bags and began checking her body temperature. When it had dropped to 28 degreesthe scientists began draining blood from its body. The monkey's blood pressure decreased and anhour later both the heart and breathing stopped; clinical death set in. For twenty minutes Keta re-mained in this state. Her temperature dropped to 22 degrees. At this point the scientists pumpedblood into its body in the direction of the heart and started artificial breathing. After two minutesthe monkey's heart became active once more. After fifteen minutes, spontaneous breathing began,and after four hours Keta opened her eyes and lifted her head. After six hours, when the scientiststried to give her a penicillin injection, Keta seized the syringe and ran with it around the room.Her behavior differed little from that of a healthy animal.
This passage focuses on__________.

A.the difference between biological and clinical death
B.the process of dying
C.prolonging the period of clinical death
D.the nature of clinical death