Final answer:
Human factors psychology focuses on optimizing human-environment interactions, with the correct concern being the height of the chair as it affects ergonomic comfort and long-term health.
Step-by-step explanation:
The question pertains to the field of human factors psychology, which focuses on optimizing human-environment interactions. Regarding the aspect of an office workstation a human factors psychologist would be concerned about, the correct option is a. height of the chair. This is because one of the central concerns in ergonomic design is the physical comfort and efficiency of individuals when interacting with their environment, and chair height directly relates to posture and ergonomic comfort. Improper chair height can lead to discomfort, reduced productivity, and long-term health issues such as back pain or carpal tunnel syndrome. The focus here is on creating an environment that fits the user, rather than forcing the user to adapt to the environment, which encompasses much of what human factors psychology is about.