单项选择题

Questions 28 and 29 are based on the following news. At the end of the news item, you will be given 10 seconds to answer the questions.
Now, listen to the news.

Why were the documents released

A.To improve the relationship with Russia.
B.To urge Clinton not to end the trade restriction.
C.To prove that many soldiers are still missing.
D.To provide more information about North Vietnam.