【题目】_______ in doing his homework , he didn't know I had walked in.
A.Burying
B.Buried
C.To Bury
D.To be buried

【答案】B
【解析】句意：他在专心做作业，不知道我已经走进来了。be buried in沉思，专心于，被埋葬在。这里主从句主语一致，故选B。