Complex sentence: San Diego County comprises the San Diego-Carlsbad, CA Metropolitan Statistical Area, which is the 17th most populous metropolitan statistical area and the 18th most populous primary statistical area of the United States as of July 1,2012.
Split into simpler sentences: San Diego County comprises the San Diego-Carlsbad, CA Metropolitan Statistical Area. The San Diego-Carlsbad, CA Metropolitan Statistical Area is the 17th most populous metropolitan statistical area and the 18th most populous primary statistical area of the United States as of July 1,2012.