Shortly after September 11th, President Bush’s father observed that just as Pearl Harbor awakened this country from the notion that we could somehow avoid the call of duty to defend freedom in Europe and Asia in World War Two, so, too, should this most recent surprise attack erase the concept in some quarters that America can somehow go it alone in the fight against terrorism or in anything else for that matter.

But America’s allies have begun to wonder whether that is the lesson that has been learned--or whether the Afghanistan campaign’s apparent success shows that unilateralism works just fine. The United States, that argument goes, is so dominant that it can largely afford to go it alone.

It is true that no nation since Rome has loomed so large above the others, but even Rome eventually collapsed. Only a decade ago, the conventional wisdom lamented an America in decline. Bestseller lists featured books that described America’s fall. Japan would soon become "Number One". That view was wrong at the time, and when I wrote "Bound to Lead" in 1989, I, like others, predicted the continuing rise of American power. But the new conventional wisdom that America is invincible is equally dangerous if it leads to a foreign policy that combines unilateralism, arrogance and parochialism.

A number of advocates of "realist" international-relations theory have also expressed concern about America’s staying-power. Throughout history, coalitions of countries have arisen to balance dominant powers, and the search for traditional shifts in the balance of power and new state challengers is well under way. Some see China as the new enemy; others envisage a Russia-China-India coalition as the threat. But even if China maintains high growth rates of 6% while the United States achieves only 2%, it will not equal the United States in income per head until the last half of the century.

Still others see a uniting Europe as a potential federation that will challenge the United States for primacy. But this forecast depends on a high degree of European political unity, and a low state of transatlantic relations. Although realists raise an important point about the leveling of power in the international arena, their quest for new cold-war-style challengers is largely barking up the wrong tree. They are ignoring deeper changes in the distribution and nature of power in the contemporary world. The paradox of American power in the 21st century is that the largest power since Rome cannot achieve its objectives unilaterally in a global information age.

What is realists’ attitude towards the continuing rise of American power（）

A. Apprehensive

B. Boastful

C. Optimistic

D. Grieved