问题如下图：
选项：
A. 
B. 
C. 
解释：
根据题意，company3，没有unit root。可以说等同于covariance-stationary吗？或者说company3有什么地方使其不能满足条件？
NO.PZ201709270100000508 Company #2 Company #3 B is correct. When two time series have a unit root but are co-integrate the error term in the lineregression of one time series on the other will covarianstationary. Exhibit 5 shows ththe series of stoprices of Company #2 anthe oil prices both contain a unit root, anthe two time series are co-integrate a result, the regression coefficients anstanrerrors are consistent ancusefor hypothesis tests. Although the cointegrateregression estimates the long-term relation between the two series, it mnot the best mol of the short-term relationship. 假如company 3: no unit root, no sericorrelation ,是否就可以选择了
Exhibit 5 shows ththe series of stoprices of Company #2 anthe oil prices both contain a unit root, anthe two time series are co-integrate 请问 如何通过Exhibit 5 看出来他们含有单位根？
Company #2 Company #3 B is correct. When two time series have a unit root but are co-integrate the error term in the lineregression of one time series on the other will covarianstationary. Exhibit 5 shows ththe series of stoprices of Company #2 anthe oil prices both contain a unit root, anthe two time series are co-integrate a result, the regression coefficients anstanrerrors are consistent ancusefor hypothesis tests. Although the cointegrateregression estimates the long-term relation between the two series, it mnot the best mol of the short-term relationship. 题目问的是什么意思？没看懂
company #3没有unit root，就算X、Y之间不协整，也可以做多元回归分析吧？
请问company1之所以不入选和他有arch现象有联系么？判断三家公司都不constant的点是在他们都有 sericorrelation of error term的缘故么？从哪里可以看出有过单位根的情况？
