Lucy: Do you know this ____.
Bob: Yes.
Lucy: Who' s she?
Bob: She's my ____.
Lucy: What's she like?
Bob: She is ____.
Lucy: Is she ____?
Bob: No, she isn't.
Bob: Yes, she is.
下列各项中,属于腔肠动物和扁形动物的共同特征的是( )
信号传送过程中,与无线电广播最相似的是