题目内容：
根据下面资料，回答题 In Melbourne, Australia, not long ago specialists gave advice on a patient's problem.
There's nothing unusual in that except that the patient was in the far west of New South Wales at the time. That's hundreds of miles from Melbourne. The heart disease experts were able to make their diagnosis after listening to the patient's heartbeat over the telephone.
They were testing a new device that can change readings of a patient's heartbeat into tone signals that can be sent by telephone. The device was designed in Australia. It is meant for use in areas far from large cities. Doctors in remote areas can take the heartbeat readings right in the patient's home. Then they can play them over a telephone line to specialists in larger centers. The doctor in the remote area is thus able to get an expert's opinion on the heart condition of his patient. Experiments with the device show that the whole process takes only a few minutes.
This article is mainly about a device for A．preventing heart disease
B．sending medical information
C．moving heart patients
D．recording doctors' conversations
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