What is one advantage of solar space heating? 

A)  It produces only moderate levels of carbon dioxide additions to the atmosphere. 
B)  It is free to construct. 
C)  There are well-developed active and passive technologies to choose from. 
D)  It produces low-to-moderate net useful energy.

One advantage of solar space heating is that there are well-developed active and passive technologies to choose from. This means that there are a variety of options available for implementing solar space heating systems, and they have been tested and developed over time to optimize efficiency and effectiveness. Option A is not necessarily true for all types of solar space heating systems, as some may still have significant carbon dioxide emissions related to manufacturing and installation. Option B is not accurate, as there will still be costs associated with constructing and installing solar space heating systems. Option D is not a clear advantage, as low-to-moderate net useful energy may not be sufficient for some heating needs.