In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
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Question: What led to the result that observers in relative motion measure different elapsed times?, Context: In non-relativistic classical mechanics, Newton's concept of "relative, apparent, and common time" can be used in the formulation of a prescription for the synchronization of clocks. Events seen by two different observers in motion relative to each other produce a mathematical concept of time that works sufficiently well for describing the everyday phenomena of most people's experience. In the late nineteenth century, physicists encountered problems with the classical understanding of time, in connection with the behavior of electricity and magnetism. Einstein resolved these problems by invoking a method of synchronizing clocks using the constant, finite speed of light as the maximum signal velocity. This led directly to the result that observers in motion relative to one another measure different elapsed times for the same event.

Answer: a method of synchronizing clocks

Question: What else should be watched for?, Context: Shortness of breath occurs when the damage to the heart limits the output of the left ventricle, causing left ventricular failure and consequent pulmonary edema. Other symptoms include diaphoresis (an excessive form of sweating), weakness, light-headedness, nausea, vomiting, and palpitations. These symptoms are likely induced by a massive surge of catecholamines from the sympathetic nervous system, which occurs in response to pain and the blood flow abnormalities that result from dysfunction of the heart muscle. Loss of consciousness (due to inadequate blood flow to the brain and cardiogenic shock) and sudden death (frequently due to the development of ventricular fibrillation) can occur in MIs.

Answer: Other symptoms include diaphoresis (an excessive form of sweating), weakness, light-headedness, nausea, vomiting, and palpitations

Question: Where is Qixia District?, Context: A number of sculptural ensembles of that era, erected at the tombs of royals and other dignitaries, have survived (in various degrees of preservation) in Nanjing's northeastern and eastern suburbs, primarily in Qixia and Jiangning District. Possibly the best preserved of them is the ensemble of the Tomb of Xiao Xiu (475518), a brother of Emperor Wu of Liang. The period of division ended when the Sui Dynasty reunified China and almost destroyed the entire city, turning it into a small town.

Answer:
Nanjing