Answer:
d. temporary
Explanation:
Competitive advantage refers to a competitive edge a firm gains over it's competitors by offering better value via it's products or by offering such products at reduced prices.
Competitive advantage results out of a unique or specific methods of production which is more efficient than the competitors and most importantly which cannot be imitated by competitors.
In the given case, the advantage which has accrued is on account of organic method of raising chickens and organic seasonal produce. These advantages are momentarily as, soon other restaurants shall follow suit and gradually these shall disappear.
