Recent investigations of earthquakes have turned up a previously unknown type of seismic shock, known as a displacement pulse, which is believed to be present in all earthquakes. Alarmingly, high-rise buildings are especially vulnerable to displacement pulses, according to computer models. Yet examination of high-rises within cities damaged by recent powerful earthquakes indicates little significant damage to these structures. Which one of the following, if true, contributes to a resolution of the apparent paradox? ['Computer models have been very successful in predicting the effects of other types of seismic shock.', 'Scientific predictions based on computer models often fail when tested in the field.', 'The displacement pulses made by low- and medium-intensity earthquakes are much less powerful than those made by the strongest earthquakes.', 'While displacement pulses have only recently been discovered, they have accompanied all earthquakes that have ever occurred.']