Answer:
b)
Step-by-step explanation:
Sensitive issues refer to topics which people tend to feel uncomfortable talking about (Like harassment, addictions, violence)
Many studies on this topic have shown that when people are in front of other person who's interviewing them they might hide some aspects of themselves to create a better impression on the interviewer, therefore, the information acquired this way is not 100% right.
Regarding sensitive issues, it is even more difficult for people to talk about them specially when it comes to an stranger (like a researcher). Thus, it is not recommended to address sensitive issues in interviews but rather by self-administered questionnaires in which the person doesn't have to interact with another person.
When it comes to complicated issues, a questionnaire is not recommended since it could leave the researcher without enough information, and since it's a complicated issue, the researcher might want to be there to clarify people's answers. Therefore, for complicated issues, it is better to use interviews.
Thus, the correct answer is b) Use self-administered questionnaires for sensitive issues and interviews for complicated issues