Suppose the population regression is of the form: Y=PXat...+ Boxkata, +up. i=1,.., n, f= 1..., T. where X1 x is the value of the first regressor for entity / in time period , X2, is the value of the second regressor, and so forth; and ay,..(I, are entity-specific intercepts. Which of the following statements is true in describing the fixed effects regression assumptions? O A. The variables for one entity are distributed identically to, but independently of, the variables for another entity and also within an entity; that is, the variables are i.i.d. across and within entities for i = 1..., n, t= 1.... T. O B. The error term has a zero conditional mean across entities but a non-zero conditional mean within entities. O C. The variables for one entity are distributed identically to, but independently of, the variables for another entity, that is, the variables are i.i.d. across entities for i = 1..., n. O D. The variables for one entity are distributed identically to, but independently of, the variables within an entity; that is, the variables are i.i.d. within entities for t = 1,... T. Which of the following statements is true in describing clustered standard errors? O A. Clustered standard errors allow for arbitrary autocorrelation within an entity, but treat the errors as homoskedastic and uncorrelated across entites. O B. Clustered standard errors allow for heteroskedasticity and arbitrary autocorrelation within an entity, but treat the errors as uncorrelated across entities. O C. Clustered standard errors allow for arbitrary autocorrelation within and across entities, but treat the errors as homoskedastic within and across entities. O D. Clustered standard errors allow for heteroskedasticity within an entity, but treat the errors as uncorrelated within and across entities