题目内容：
阅读下面短文，掌握其大意，然后从各题所给的四个选项(A、B、C和D)中，选出最佳选项。Lightning flashed through the darkness over Sibson's bedroomskylight(天窗)．Sibson was shaken by a clap of thunder __16__ he knew what washappening．The storm had moved directly__ 17__ his two-story wooden house．Then he heard the smoke alarm beeping．
Sibson rushed down the stairs barefoot to __18__ ; he opened the door to the basement(地下室), and flames __19 __out．Sibson ran backupstairs to call 911 from his bedroom．"I felt __20__ because the room had a separate outdoor stairway," he explains．
But the phone didn't work, and when he tried to go down the out door stairway, he was __21__by a wall of flames．Sibson realized he wastrapped(困住)．
Sibson's house was three kilometers __22 __the main road and was so well hidden by trees that he knew calling for help would be __23__ Upa hill nearby lived Sibson's neighbor, Huggons．He was lying in bed when something like a smoke alarm __24__ his ears．He jumped out of bed, took his __25__ and flashlight, and headed down the hillside toward the __26__．That was when he saw the rolling heavy smoke．
Huggons dialed 911, and the operator warned him not to__ 27__ the house．But Huggons said,
"There is no way I am going to listen to Sibson __28 __and die in that fire．"
"Anyone there?" Huggons called out．Then he heard"Help ! I'm trapped !" coming from the second floor balcony(阳台)．He entered the house, but soon had to run back to catch his __29__ After one more __30 __inside the house, Huggons gave up and __31__ around back．
The wind parted the smokejust __32__ for him to catch sight of Sibson．But there was no way to get to him．He __33__ the flashlight into the woods and noticed a ladder．He took it over to the halcony and__ 34__ Sibson down just as the second floor of the house fell off．
Sibson is still __35__ when he tells the story．" I was alone that night," he says．"Then I heard the most beautiful sound in my life．It was Huggons．"
__________ A．before
B．while
C．since
D．until
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