Which method is used to solve for coefficients b0, b1, .., bn in your linear regression model ?

Which method is used to solve for coefficients b0, b1, .., bn in your linear regression model ?
Y = b0 + b1x1+b2x2+….+bnxn

A.
Ordinary Least squares

B.
Apriori Algorithm

C.
Ridge and Lasso

D.
Integer programming