A:a≥1
B:a>1
C:a≤﹣1
D:a<﹣1
This is a cat.
It's my pet.
Her name is Lylie.
She's clever.
She likes fish.
I like her very much.
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对达尔文自然选择学说解释错误的是( )
下列各图描述的实验中,用来说明声音的传播需要介质的是( )