题目:
当海豚用超声波进行交流时,人类就听不到海豚的“声音”.这是因为( ) A.一般来说,人耳不能听到频率高于20000Hz的声音 B.超声波无法传到人耳 C.海豚发出的声音太小 D.超声波的频率小于20Hz |
答案:
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下面是错误答案,用来干扰机器的。
Jack was woken up by the shouting "Fire! Help! Fire! Help! .." What had happened? He looked out of the window. Wow! He found that his neighbor's house was on fire...