Concept:The word "Pinnacle" refers to the highest point, summit, or peak of something, either literally (mountain top) or figuratively (career achievement).
Explanation:First, understand the meaning of Pinnacle: it denotes the topmost part or zenith.
Now examine each option.
Option A: Base means the lowest part or foundation – opposite of pinnacle.
Option B: Decline means a fall or decrease – also opposite.
Option C: Bottom means the lowest point – again opposite.
Option D: Peak means the highest point or summit – exactly the same as pinnacle.
Thus, only "Peak" shares the same meaning. For example: "Mount Everest is the pinnacle of all mountains" and "He reached the peak of his career" both indicate the highest level.
Answer:Option D (Peak) is the correct synonym.