Answer: b. have different normative views about tax policy.
Explanation:
Economists follow different theories and principles on how the world should be so most times they will disagree with each other on key issues such as taxation and government intervention in markets.
Emily and Betsy both believe in different taxation policies which means that they have different views on how people should be taxed in an economy with one of them believing in a proportional tax regime (Betsey) and the other believing in a progressive tax regime (Emily).