Final answer:
The subject of this question is Social Studies, and the answer is cul-de-sac.
Step-by-step explanation:
The subject of this question is Social Studies, as it pertains to the understanding of local service streets and their impact on through traffic. Specifically, it involves the categorization and identification of different types of streets based on their characteristics.
The correct answer to the question is a. Cul-de-sac. A cul-de-sac is a dead-end street with only one entrance, making it non-conducive to through traffic. It often ends in a circular area or turnaround.