题目内容：
请阅读Passage 1，完成题：Modern scientists divide the process of dying into two stages--clinical or temporary death and biological death. Clinical death occurs when the vital organs, such as the heart or lungs, have ceased 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 cells and tissues. Death is then irreversible and final.
Scientists have been seeking a way to prolong the period of clinical death so that the organism can be revived before biological death occurs. The best method developed so far involves cooling of the organism, combined with narcotic sleep. By slowing down the body's metabolism, cooling delays the processes leading to biological death.
To illustrate how this works, scientists performed an experiment on a six-year-old female monkey called Keta. The scientists put Keta to sleep with a narcotic. Then they surrounded her body with ice-bags and began checking her body temperature. When it had dropped to 28 degrees the scientists began draining blood from its body. The monkey's blood pressure decreased and an hour later both the heart and breathing stopped; clinical death set in. For twenty minutes Keta remained in this state. Her temperature dropped to 22 degrees. At this point the scientists pumped blood into its body in the direction of the heart and started artificial breathing. After two minutes the 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 scientists tried 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
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