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单项选择题The first paragraph mentions three ways of activating the saliva in the mouth.

A． Right
B． Wrong
C． Not mentioned

单项选择题Which of the following is discussed in the third paragraph

A．The same noise level produces a different effect on land and in the ocean.
B．Different places may have different types of noises.
C．The decibel is not a suitable unit for measuring underwater noise.
D．Different ocean animals may have different reactions to noises.