Scientists propose placing seismic stations on the floor of the Pacific Ocean to warn threatened coastal communities on the northwestern coast of the United States of approaching tidal waves caused by earthquakes. Since forewarned communities could take steps to evacuate, many of the injuries and deaths that would otherwise occur could be avoided if the government would implement this proposal. The answer to which of the following questions would be most important in determining whether implementing the proposal would be likely to achieve the desired result? ['How soon after a tidal wave hits land is it safe for evacuees to return to their communities?', 'Would there be enough time after receiving warning of an approaching tidal wave for communities to evacuate safely?', 'When was the last time that the coastal communities were threatened by an approaching tidal wave?', 'Can the stations be equipped to collect and relay information about phenomena other than tidal waves caused by earthquakes?']