阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 Scientists Develop Ways of Detecting Heart Attack German researchers have (1) a new generation of defibrillators and early warning software aimed at offering heart patients greater protection (2) sudden death from cardiac arrest. In Germany alone around 100,000 people die annually as a result of cardiac arrest and many of these cases (3) by disruption to the heart’s rhythm. Those most at risk are Patients who have (4) suffered a heart attack and for years the use of defibrillators has proved useful in diagnosing (5) disruptions to heart rhythms and correcting them automatically by intervening within seconds. These devices (6) a range of functions such as that of pacemaker. Heart specialists at Freiburg’s University Clinic have now achieved a breakthrough with all implanted defibrillator (7) of generating a six-channel electrocardiogram(ECG) within the body. This integrated system allows early diagnosis of (8) blood-flow problems and a pending heart attack. It will be implanted in patients for the first time this year. Meanwhile, researchers at the Fraunhofer Institute for Applied Mathematics in Kaiserslautern have developed new computer software that renders the evaluation of ECG data (9) . The overwhelming (10) of patients at risk will not have an implanted defibrillator and must for this reason undergo regular ECGs. "Many of the current programs only (11) into account a linear correlation of the data. We are, however, making use (12) a non-linear process that reveals the chaotic patterns of heart beats as an open and complex system." Hagen Knaf says." (13) changes in the heart beats over time can be monitored and individual variations in patients taken into account." An old study of ECG data, based (14) 600 Patients who had suffered a subsequent heart attack, enabled the researchers to compare risks and to show (15) the new software evaluates the data considerably better.

A. are caused
B. caused
C. are to cause
D. have been causing