One Sunday, Mark decided to go sailing in his boat with his friend Dan, but Dan happened to be away. Dan's brother John offered to go instead though he did not know anything about sailing. Mark agreed and they set out to sea. Soon they found themselves in a thick fog. Mark was sure they would be hit by a big ship. Fortunately he saw a large buoy (浮标) through the fog and decided to tie the boat to it for safety. As he was getting onto the buoy, however, he dropped the wet rope. The boat moved away in the fog carrying John, who did not know how to use the radio, He drifted (漂流) about and was not seen until twelve hours later. Mark spent the night on the buoy. In the early morning he fell asleep. He was having a bad dream when a shout woke him up. A ship, the Good Hope, came up and he climbed onto it and thanked the captain. The captain told him that John had been picked up by another ship and the ship's captain had sent out a message. "Without the message I would not have found you on the buoy." he said.
单选题
Mark tried to tie the boat to the buoy so that ______.
【正确答案】
C
【答案解析】第二段中讲到，Mark和John在海上遇到了大雾，Mark担心大轮船会撞到他们，这时他发现了一个浮标，“and decided to tie the boat to it for safety.”这样，船就不会撞到他们了。所以本题的正确答案是C。
单选题
John and Mark became separated because ______.
【正确答案】
B
【答案解析】从第二段的最后几句可以看出“The boat moved away in the fog carrying John, who did not know how to use the radio. He drifted about…”另外，第一段也告诉我们John根本不懂航海。由此可见选项B是正确答案。
单选题
What made it possible for Mark to be found on die buoy?
【正确答案】
A
【答案解析】Mark被一艘船救起后，船长解释说“…．John had been picked up by another ship and the ship's captain had sent out a message”根据这句话我们可以推断出John被救后告诉了人们Mark在浮标上，所以Mark才能得救。而在第二段中已经告诉我们John不会使用无线电，所以选项B是错误的，而A是唯一的正确答案。
单选题
The word "he" in the last sentence refers to ______.