In the Context of Empirical Research on Compensating Differentials, Omitted

In the context of empirical research on compensating differentials, omitted variable bias may exist when:

A) Important variables are not controlled for in the measurement of the wage-risk tradeoff.
B) Irrelevant variables are included in the equation.
C) Employers attempt to hide crucial safety information from their employees.
D) The information about factors that are correlated with job risk is imperfect.
E) Samples have selection issues.