Concept:The idiom "to close ranks" means that a group of people comes together or unites, especially to support one another when facing opposition or criticism.
Explanation:The phrase comes from the military practice of soldiers closing up their lines to make a stronger defensive formation.
In daily language, it suggests unity, solidarity, and standing shoulder to shoulder with others.
Option A is incorrect because fierce competition is about opposing sides, while closing ranks is about cooperation.
Option B is incorrect because the idiom does not mean avoiding colleagues; it means drawing closer to them.
Option C is incorrect because the phrase has nothing to do with hiring practices or employment policies.
Option D is correct because it exactly conveys the idea of uniting to protect a common interest or shared goal.
Answer:D. To unite in order to defend a common interest