[A] continuous
[B] continual
[C] unceasing
[D] gradual
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Why are there two teams to study the same ice?
[A] Because they belong to different countries.
[B] Because they compete against each other.
[C] Because they want to confirm their findings.
[D] Because there are too many ices for only one team.
At which frequency is the sound audible to human beings?
[A] Fewer than about 20 vibrations per second.
[B] More than about 20,000 vibrations per second.
[C] About in a range of 20 and 20,000 vibrations per second.
[D] 120 vibrations per second.