听下面一段材料,回答第1-4题. 1．What does Obama's victory mean? A．He has become the 41st President of the United States. B．He's become USA's first black Presidentelect. C．He will be the first AfricanAmerican in the US history. 2．Which is NOT mentioned as a serious challenge for Obama? A．Civil wars. B．Weather change. C．Financial crisis 3．When did Obama exercise his duty as President? A．On January 20,2009. B．On January 12,2009. C．Right after the election. 4．Which of the following best describes how Obama felt in his victory speech? A．Dependent and joyless. B．Hopeful and confident. C．Proud and over optimistic