单项选择题
A.上下端各1个点B.上下端各2个点C.上下中端各1个点D.上下中端各2个点
A.+2.0,-3.0B.+5.0,-2.0C.+3.0,-2.0D.+3.0,-3.0
A.+5.0,-3.0B.+5.0,-2.0C.+3.0,-2.0D.+3.0,-3.0