Passage 2Yet in its current 【dour】 mood, Europe risks almost ove

Passage 2
Yet in its current 【dour】 mood, Europe risks almost overlooking the 【revolutionary 】step forward it has taken in creating the world’s largest and wealthiest barrier—free market?and on a continent where, for centuries, economic battles have led to some of history’s bloodiest wars. Moreover, a failure to reinforce the single market by pushing forward with European integration could lead to an unraveling of what the internal market program has achieved, some observers say.
41.What did some observers think might cause the failure of the internal market program?
【正确答案】：failure to reinforce the single market by pushing forward with European integration.