Some people have suggested to a city government that a sprinkler that fires automatically in the event of a fire should be installed in all newly built houses. However, a real estate developer believes that since 90% of the houses' fires were extinguished by family members, they were installed indoors. Automatic sprinklers have little meaning for fire fighting. Which of the following, if true, would most weaken the views of real estate developers? ["most people don't have formal training in fire fighting skills.", 'it is much cheaper to install a smoke detector in a home than a sprinkler.', "the time for the city's fire brigade to the fire scene is shorter than the national average.", 'most of the property damage caused by the fire in the house was because family members were not present at the time of the fire.']