In solving a linear programming minimization problem using the simplex method

Select one:

a$.$

every time a surplus variable is subtracted, an artificial variable must be added.

b$.$

every time a surplus variable is added, an artificial variable must be subtracted.

c$.$

every time an artificial variable is added, a surplus variable must be subtracted.

d$.$

every time a surplus variable is added, an artificial variable must be added.