Which of the Following Is True

Multiple Choice

Which of the following is true?

A) A variable has a causal effect on another variable if both variables increase or decrease simultaneously.
B) The notion of 'ceteris paribus' plays an important role in causal analysis.
C) Difficulty in inferring causality disappears when studying data at fairly high levels of aggregation.
D) The problem of inferring causality arises if experimental data is used for analysis.