问题补充：
After being elected President of United States, Barack Obama moved with his family into White House.
A. /; the; /
B. /; the; the
C. the; /; /
D. /; an; the
答案：
A. /; the; /
(答案→)B. /; the; the
C. the; /; /
D. /; an; the
解析：考查冠词，第一空不填，Presiden这样表示职位的词做补足语，同位语时，不加冠词，第二空填the，特指美国，第三空填the，特指白宫。句意是：在当选美国总统之后，奥巴马和家人搬进了白宫。选B。
