This method of collecting observations is best described as Survey using interview method.
Option: (c)
Explanation:
Interview is a conversation that is especially structured where one participant ask question and another participants give answer.
The person who ask question is called interviewer and the person who respond to the question is called interviewee.
Interview is face to face conversation. In the above given case, psychologist is a interviewer who might intend to get information about the job like  facility, working condition, incentives and the local workers’ union are the interviewee.