原题
In 2009, the US state of Montana enacted rate stability regulations (RSRs), constraining insurance companies' latitude to raise premiums (the recurring fees policyholders pay to maintain insurance policies) once policies are in effect. Although RSRs are intended to benefit consumers, Naoki Aizawa and Ami Ko note that RSRs could curtail insurers' profits to such a degree that insurers abandon the market, thereby reducing the competitive pressure that typically restrains premium prices for newly issued policies. To determine whether this occurred in Montana, students first collect data on the number of insurers in the state for a few years leading up to and following 2009 and the premium prices for new policies offered by those insurers.
Based on the text, what would be the most reasonable next step for the students to take to accomplish their goal?
ACompare changes over time in the premium price data the students have collected with changes over time in premium prices for policies that were already in effect during the same period in an otherwise similar state that had not enacted RSRs
BCompare changes over time within each of the two types of data the students have collected with changes over time in analogous data for the same period from an otherwise similar state that had not enacted RSRs
CCompare changes over time within each of the two types of data the students have collected with changes over time in the same types of data from Montana for a period beginning several years after 2009
DCompare changes over time in the insurer-number data the students have collected with changes over time in insurer-number data from another state that enacted RSRs but not during the same period
正确答案：B
解题思路
老师暂未填写解题思路。