To Derive the Least Squares Estimator µ_Y, You Find the Estimator

To derive the least squares estimator µ_Y, you find the estimator m which minimizes

A) $\sum _ { i = 1 } ^ { n } \left( Y _ { i } - m \right) ^ { 2 }$
B) $\left| \sum _ { i = 1 } ^ { n } \left( Y _ { i } - m \right) \right|$
C) $\sum _ { i = 1 } ^ { n } m Y _ { i } ^ { 2 }$
D) $\sum _ { i = 1 } ^ { n } \left( Y _ { i } - m \right)$