Indoor Air Pollution Could Be Sharply Reduced by

Indoor air pollution could be sharply reduced by

A) modifying building codes to prevent radon infiltration.
B) requiring exhaust hoods or vent pipes for stoves, refrigerators, or other appliances burning natural gas or other fossil fuels.
C) finding substitutes for potentially harmful chemicals.
D) using office machines in well-ventilated areas.
E) all of these answers