Houses built during the last ten years have been found to contain indoor air pollution at levels that are, on average, much higher than the levels found in older houses. The reason air-pollution levels are higher in the newer houses is that many such houses are built near the sites of old waste dumps or where automobile emissions are heavy.
Which of the following, if true, calls into question the explanation above

A．Many new houses are built with air-filtration systems that remove from the house pollutants that are generated indoors.

B．The easing of standards for smokestack emissions has led to an increase in air-pollution levels in homes.

C．New houses built in secluded rural areas are relatively free of air pollutants.

D．Warm-weather conditions tend to slow down the movement of air, thus keeping pollution trapped near its source.

E．(E) Pressboard, an inexpensive new plywood substitute now often used in the construction of houses, emits the pollutant formaldehyde into the house.

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