When I was a boy,I belonged to the Boy Scouts ,so I used to go camping every summer,and once something happened which I have never been able to explain.      We were camping in a place above a river. After arriving,we all rushed down to the river and had a swim. Standing by the river,we noticed that it was surrounded by cliffs . If someone wanted to reach the river at this point,he had to walk past our camp.     Several days later,the scoutmaster had to he away for a day. That afternoon,we had supper early. We were sitting round the fire,eating and talking,when a man walked past and went down towards the river. We all felt that this man looked very strange,but,because each of us was afraid of looking very stupid,no one said anything.     We ate rather slowly,taking as long as possible. After finishing,we collected our plates together so that we could take them to the river where we always washed them. But no one moved towards the river-- we stood looking at each other ashamed. Then all shouting at once, we began talking about the man who had walked past us. We agreed how strange he looked and we wondered what he could be doing by the river. We knew that he could only return by passing through our camp.     An hour passed. Then one of the boys suggested we should creep down by the river so that we could see what the man was doing. Moving very slowly and keeping in the shadow, we crept down towards the bank. One boy climbed a tree so that he could see everything clearly. He called to us that there was no one there,so we ran down to the bank, looking every-where carefully. We could not understand where the man had gone.     When it got dark,we went back to our camp feeling bewildered. We told the scoutmaster what had happened in the evening. Smiling,he doubted that we had seen the man,but finally suggested we go and look again. We did,but there was no one there. Many years have passed,but I still remember it as if it were yesterday. What did we see?I do not know. The writer still remembers the event because  _  .
the boys acted foolishly the camping place is beautiful there has been no explanation for the event he particularly enjoyed his camping that summer.
Question: When I was a boy,I belonged to the Boy Scouts ,so I used to go camping every summer,and once something happened which I have never been able to explain.      We were camping in a place above a river. After arriving,we all rushed down to the river and had a swim. Standing by the river,we noticed that it was surrounded by cliffs . If someone wanted to reach the river at this point,he had to walk past our camp.     Several days later,the scoutmaster had to he away for a day. That afternoon,we had supper early. We were sitting round the fire,eating and talking,when a man walked past and went down towards the river. We all felt that this man looked very strange,but,because each of us was afraid of looking very stupid,no one said anything.     We ate rather slowly,taking as long as possible. After finishing,we collected our plates together so that we could take them to the river where we always washed them. But no one moved towards the river-- we stood looking at each other ashamed. Then all shouting at once, we began talking about the man who had walked past us. We agreed how strange he looked and we wondered what he could be doing by the river. We knew that he could only return by passing through our camp.     An hour passed. Then one of the boys suggested we should creep down by the river so that we could see what the man was doing. Moving very slowly and keeping in the shadow, we crept down towards the bank. One boy climbed a tree so that he could see everything clearly. He called to us that there was no one there,so we ran down to the bank, looking every-where carefully. We could not understand where the man had gone.     When it got dark,we went back to our camp feeling bewildered. We told the scoutmaster what had happened in the evening. Smiling,he doubted that we had seen the man,but finally suggested we go and look again. We did,but there was no one there. Many years have passed,but I still remember it as if it were yesterday. What did we see?I do not know. The writer still remembers the event because  _  .
A. the boys acted foolishly
B. the camping place is beautiful
C. there has been no explanation for the event
D. he particularly enjoyed his camping that summer.
Answer: