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 search operation commander, the recovery of the missing Americans is slowed down because（）
A．the weather conditions are unfavorable.
B．the necessary documents are unavailable.
C．the sites are inaccessible.
D．some local people are greedy.