The passage given below is followed by four alternate summaries. Choose the option that best captures the essence of the passage.

As Soviet power declined, the world became to some extent multipolar, and Europe strove to define an independent identity. What a journey Europe has undertaken to reach this point. It had in every century changed its internal structure and invented new ways of thinking about the nature of international order. Now at the culmination of an era, Europe, in order to participate in it, felt obliged to set aside the political mechanisms through which it had conducted its affairs for three and a half centuries. Impelled also by the desire to cushion the emergent unification of Germany, the new European Union established a common currency in 2002 and a formal political structure in 2004. It proclaimed a Europe united, whole, and free, adjusting its differences by peaceful mechanisms.

The passage begins by highlighting Europe's continual attempt to adapt itself in a multipolar world by striving to be a dynamic entity- nationally and internationally{"changed its internal structure and invented new ways of thinking about the nature of international order"}.  Post this, the author portrays how certain stimuli in the modern world has lead Europe to review its political components {"set aside the political mechanisms through which it had conducted its affairs for three and a half centuries"} and to make changes in its economic structure {"established a common currency "}. Thus, the passage presents two key elements: (1) the fact that Europe has consistently tried to adapt to a changing world and (2) the manner in which Europe has attempted to achieve that in the existing multi-polar setup. Option D correctly highlights these points.

Option A: This misses out on the point (2). Furthermore, directly ascribing the unification of Europe to its attempt to rapidly change would be incorrect. 

Option B: This does not fully capture the essence of the passage and misses out on point 1.

Option C: Although the statement in this option captures point 1, it misses out on point 2.

Hence, Option D is the correct answer.