In Modeling a Traveling Salesman Problem, Let $X_{\mathrm{ijk}}$ Be a 0-1 Decision Variable, Which Takes a Value of 0-1

In modeling a traveling salesman problem, let $X_{\mathrm{ijk}}$ be a 0-1 decision variable, which takes a value of 0 if in the kth leg the tour corresponding to the solution does not go from node $\mathrm{i}$ to node $\mathrm{j}$ . $\mathrm{X}_{\mathrm{ijk}}$ is set to be equal to 1 if the tour goes from node $\mathrm{i}$ to node $\mathrm{j}$ in the kth leg. In a problem with just 4 nodes and without loss of generality, assume that the tour starts and ends in node 1. Mark the correct constraint to make sure that the tour starts in node 1

A) $\mathrm{X}_{121}+\mathrm{X}_{131}+\mathrm{X}_{141} \leq 1$
B) $X_{121}+X_{131}+X_{141} \geq 1$
C) $X_{121}+X_{131}+X_{141}=1$
D) $X_{214}+X_{314}+X_{414}=1$