need clear explanation please

and please clarify which option is correct :)

In the minimum spanning tree problem formulation, the subtour elimination constraint can be formulated as: a. E)- =1*ij = ISI - 1, Vi, j E (1...), and i # 1 where ISI : the cardinality of subset S, and for all S CV b. none of the mentioned c. 1)(x + x) = 1 d. *+ x 2 1. V. JE ....) e. *ij + x S 1. V.JE 1...)