如图,AB是⊙O的直径,⊙O的半径3cm,弦CD⊥AB于E,∠CDB=30°,则弦CD的长为( )
— What’s your English teacher like?
—To a certain degree, she is serious but helpful.
测得一块木板的长度为1.985m,可知测量用的刻度尺的最小分度是( )