How can you improve indoor air quality?
a. keeping pets indoors as much as possible
b. using darker paint on all interior walls
c. installing sunscreens on all windows
d. increasing ventilation in enclosed spaces

The best answer is D. To improve indoor air quality, ventilation in enclosed places should be increased. Good ventilation indoors is very important in order to have good air circulation.  Also, it prevents air pollutants from affecting health and it can get rid of bad smell.

Don't pollution air circulation. wasting pollutionclean in your surroundings