单项选择题
A.1~1.5B.0.5~1C.0.7~0.9D.0.5~0.6
A.50~64%B.60~74%C.60~70%D.65~74%
A.上手纲适当长于下手纲B.上下手纲必须相等C.上手纲适当短于下手纲D.差距无影响