To provide quantitative answers to the question of |"whether reducing clam sizes can help improve elementary education'1 A} it is suicient to use common sense. B} it is suicient to look at the correlation between elementary schools] class siaes and education quality. C] is impossible since elementary education quality is not quantiable. D} we can examine empirical evidence using regression analysis. Consider the regression equation TestScore = ] +lSTrotio+ U. The disturbance term U is cap- turing A} the possible mimpecication of the mctiona] form .85 + .313Tmtio. E} factors other than studentteacher ratio [grotto]- that signicantly affect the test score {TestSco-re}. C} any possible measurement errors in the test score fTestScore]. D} all of the above. The GL5 estimator is obtained by, A} minimizing the sum of squared residuals. E} minimizing the total sum of squares. C] maximizing the HE. D} maximizing the R3. Consider the DIS estimated regression function W = \"\"15 3.5 * STroto, then for each student per teacher increase, the test seam is expected to A} increase by 3.5 points. 13} drop by 3.5 points. C} be T1215 3.5. o; be me. The 0L5 estimator will still be unbiased but no longer be the best1 if A} the independent variables are endogenous. E} the disturbance term is heteroshedastic. C] the dependent variable is binary. D} all of the above