Which is the best fitting $4$ variable model?Model #$28$ is best because it has the lowest R$?$ among the $4-$variable models.Model #$31$ is best because it has the highest Cp among the $4-$variable models.Model #$27$ is best because it has the highest R$?$ among the $4-$variable models.Model #$29$ is best because it has the lowest Cp among the $4-$variable models.