[单项选择] Heart Attack In the United States, and especially in big cities and rural areas, tens of thousands of people with hearts that should be good 【51】 to keep them alive die each year for lack of adequate first aid. In New York City, for example, a new study has shown that only one person in 100 outside of hospitals 【52】 after the heart suddenly stops pumping. In contrast, in Seattle, the survival 【53】 after such heart attacks is one in five. "The difference can be traced 【54】 the effectiveness of the chain of survival", Dr. Joseph P. Ornato said. " Each link in the 【55】 must be strong enough for many lives to be 【56】 ". The chain begins with an immediate telephone 【57】 for emergency help and the start within four minutes of the process needed for restarting the 【58】 working, by a family member or bystander (旁观者). It continues with the prompt arrival-------within eight 【59】 ten minutes of a rescuer equipped with a special instrument that
A. much
B. enough
C. many
D. too