问题补充：
The noise was so that only those with excellent hearing were aware of it.
A. dim
B. soft
C. faint
D. gentle
答案：
A. dim
B. soft
(答案→)C. faint
D. gentle
解析：faint(=weak, indistinct; not clear)“微弱的，模糊的，不清楚的”。Dim(=not bright, not clearly to be seen)不亮的，看不清的；the dim light of a candle(微弱的烛光)。
f
