In a BIP Problem with 3 Mutually Exclusive Alternatives,x₁ ,X₂

In a BIP problem with 3 mutually exclusive alternatives,x₁ ,x₂ ,and x₃,the following constraint needs to be added to the formulation:

A) x₁ + x₂ +x₃ ≤ 1
B) x₁ + x₂ +x₃ = 1
C) x₁ - x₂ -x₃ ≤ 1
D) x₁ - x₂ -x₃ = 1
E) None of the above