The correct answer is C. Causal analysis.
Causal analysis is incredibly hard to infer because it requires us to understand the relationship between two or more variables. In order to do this, we need to be able to control for other variables that could be affecting the relationship. This is often very difficult to do, especially in real-world settings.
Exploratory analysis is the process of looking at data to see what patterns or trends emerge. This type of analysis is not as concerned with making inferences about cause and effect as it is with simply describing the data.
Inferential analysis is the process of using data to make inferences about a population. This type of analysis is more concerned with making generalizations about the population than it is with describing the data.
Mechanistic analysis is the process of understanding how something works. This type of analysis is often used in the physical sciences, but it can also be used in other fields, such as economics.
In conclusion, causal analysis is the most difficult type of analysis to infer because it requires us to understand the relationship between two or more variables.