【单选题】在平面磨床上磨削一平板,要求保证其高度尺寸,一般应限制工件的( )几个自由度。To grind a flat plate on a surface grinder, its height and size should be guaranteed. Generally, how many degrees of freedom should be limited?
【单选题】In a contingency table a sample of 400 people is classified by gender and four hair colors (blond, brown, black, and red). How many degrees of freedom are there?