When a researcher wants to examine the relative effectiveness of treatments for various types of clients, settings, or contexts in order to analyze which treatments work with which types of clients, they can utilize:

A) the parametric strategy.
B) the common factor control group design.
C) the moderation design.
D) the dismantling strategy.

The moderation design allows researchers to examine the effectiveness of treatments for different types of clients, settings, or contexts by analyzing which treatments work best with which types of clients. This design looks at the interaction between the treatment and the moderating variable (client, setting, or context) to determine the effectiveness of the treatment in different situations. The parametric strategy and dismantling strategy do not specifically address this research question, and the common factor control group design is not designed to examine treatment effectiveness for different types of clients or contexts.