(As) secretary of transportation, he worked to help the (bankrupt railroads) in the northeastern (United States) (solved) their financial problems.
A.As
B.bankrupt railroads
C.United States
D.solved

A.A.As
B.bankrupt
B.United

【参考答案】

D
解析：改为solve。help sb. do sth. 固定结构，意为“帮助某人做某事”。