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Which of the following statements is NOT true according to the passage？
A. In the past, people sometimes plugged their ears to fight against the offending noise.
B. An active noise-cancellation system follows the principle of a wave being flattened by meeting its exact opposite.
C. The first active noise-cancellation system was made in the 1930s.
D. Active noise-cancellation systems are now available on the market.
According to the passage, an active noise-cancellation system______.
A. contains noise rather than negates it
B. eliminates noise rather than muffles it
C. deflects noise rather than baffles it
D. holds noise back rather than stifles it
设有关系模式：系(系号，系名，办公电话)和学生(学号，姓名，性别，所在系号)。下表是数据的物理存储示意图：
下列文件中，数据存储形式与上表中的存储形式相符的是
A. 堆文件
B. 顺序文件
C. 散列文件
D. 聚集文件
Judging from the context, the phrase "hand-to-mouth" (Line 2, Para. 5) most probably means______.
A. adventurous
B. unhappy
C. wandering
D. unstable
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