Red door

The answer to the previous question is A. A heliostat is any device that tracks the movement of the sun to reflect light. Heliostats can be used for daylighting (bringing natural light indoors) or to concentrate the sun's light to make heat to turn a steam turbine.

Next question: These blower doors are used for:

A. testing a home's air leaks during an energy audit.

B. airing out a home after a cigar-heavy poker game.

Answer and new question on next page.