Final answer:
In the sentence, 'echelons' is the correct word choice as it refers to hierarchical levels, particularly in an organization or profession like politics. It signifies ranks within a structure, most fitting for the context of the sentence.
Step-by-step explanation:
The breaking news story concerned corruption among the highest echelons of politics. The term 'echelons' correctly fits in the provided sentence as it refers to a level or rank in an organization, a profession, or society, especially with a military connotation. The other choices, 'pinnacle', 'tiers', and 'plateau', do not correctly fit the context of the sentence. 'Pinnacle' refers to the most successful point; the peak or apex. 'Tiers' are levels or layers, but do not specifically convey the upward ranking connotation. 'Plateau' typically refers to an area of relatively level high ground or a state of little or no change following a period of activity or progress, which does not fit the context of hierarchal position in politics.