Which of a Through D Is Not a Perturbation or Stress

Which of A through D is not a perturbation or stress to the equilibrium position of an endothermic chemical reaction that involves one or more gases? If all are perturbations, choose E.

A) adding reactants to a gas or solution reaction
B) removing products from a gas or solution reaction
C) decreasing the temperature
D) increasing pressure by adding an inert gas to a reaction in the gas phase
E) All of the above are perturbations to chemical equilibrium.