Final answer:
For spam filtering of emails, both supervised and unsupervised data mining techniques are used. The correct option is D.
Step-by-step explanation:
For the spam filtering of emails, you would typically use both supervised and unsupervised data mining techniques. Supervised data mining involves training a model on a labeled dataset where the emails are already marked as 'spam' or 'not spam'. Then, the model learns to classify new emails based on this training. Unsupervised data mining could involve clustering techniques to find patterns and group similar items together, which could also be applicable in identifying spam emails by grouping them with similar known spam messages.
Regarding the survey design questions, the manager of a department store conducting interviews with all employees in four randomly selected departments is using a cluster sampling design because they are selecting entire groups or clusters of employees to be surveyed. In the case of the health club asking every tenth customer on a specified day to complete a survey, the sampling design is systematic sampling as they are using a fixed sampling interval (every tenth customer) to select participants for the survey.