Which of the Following Is Not a Constraint Found in a Transshipment

Which of the following is not a constraint found in a transshipment model?

A) Constraints that ensure that the sum of units from all warehouses delivered to stores is greater than or equal to the demands in each destination
B) Constraints that ensure that the sum of units to all warehouses originating from each plant is less than or equal to the available units in that plant
C) Constraints that ensure that the amount of units entering each warehouse is equal to the amount of units leaving the warehouse
D) Constraints that ensure that the sum of units from all warehouses delivered to stores is less than or equal to the demands in each destination
E) Non-negativity constraints