[单项选择]

In November, 1969, I was working for the federal government in Champaign, where I was a security guard at their Nike Hercules Missile Base. The base, located on Lake Shore Drive near Chicago, was surrounded by water and rock-filled banks. It was my job to check all the guard points, making sure the base was secure.
When I arrived late one afternoon at the security office for my shift, I noticed a warning posted on the boards: large parts of the fencing on the west side of the lake had been cut and not yet repaired. I immediately called my supervisor Colonel Stabler in Champaign to report the problem. In response, Colonel Stabler told me to act as a sentinel relief man and double-check all stations. As each guard reported in, I would re-walk the area to see if the guard had missed anything.
As night came on, there was a misty rain, and the fog from the lake began forming a heavy cloud around the area, limiting vision to a few feet. At 11:45 p. m. , one of the guard
A. He should re-walk the areas where the fencing had been cut.
B. He should check all the guard points before the guard went off duty.
C. He was to double-check the stations of sentinels who went off duty.
D. He was to repair those parts of the fencing that had been cut.