Nike May Build a Factory at Millville (Y₁) or It $\le$

Nike may build a factory at Millville (Y₁) or it may not.It may also build a regional warehouse at the same site (W₁) .But Nike will not build a warehouse without also building a factory.So, its choices are: (1) neither factory nor warehouse; (2) factory only; or (3) factory and warehouse.The appropriate linear constraint to express this is:

A) Y₁ - W₁ $\le$ 1
B) Y₁ + W₁ $\le$ 1
C) Y₁ + W₁ $\le$ 0
D) Y₁ - W₁ $\ge$ 0