【单选题】旋转零件的重心不在旋转轴线上,当其旋转时只产生垂直旋转中心的离心力,此种现象称为( )。
【单选题】—Listen! Our music teacher is playing the music of Two Butterflies. —_________!
【简答题】—Listen! Who is singing?—It's Betty.She has a sweet( ).A. sound B. voice C. noise D. speech
【单选题】The girl has a sweet _____ ,and many people love to listen to her song.
【单选题】Listen! ______ sweet voice she has!
【单选题】Listen! The music _________ sweet.
【单选题】旋转零件的重心在旋转轴线上,当其旋转时只产生垂直旋转中心的离心力,此种现象称为()。