Final answer:
A graduate student guest lecturing an introductory sociology course would most likely address the class from a podium. Podiums are designed for such purposes and are commonly found at the front of classrooms and lecture halls.
Step-by-step explanation:
A graduate student addressing an introductory sociology course as a guest lecturer is most likely to address the class while standing at b) A podium. Podiums are common fixtures in classrooms and lecture halls, typically positioned at the front, where they provide a platform for speakers to place their notes and have a commanding view of the class. This setup facilitates engagement with the students, allows the lecturer to maintain eye contact, and helps in projecting their voice. Furthermore, podiums often house necessary audio-visual equipment to aid in the presentation.