单项选择题
Questions 13 to 15 are based on the following news. At the end of the news item, you will be given 45 seconds to answer the three questions. Now listen to the news
According to the news, Vietnam may be willing to help America mainly because of（）
A．its changed policy towards America.
B．recent international pressure.
C．its desire to have the US trade embargo lifted.
D．the impending visit by a senior US military officer.