若am=6,an=3,则am﹣n=____.
已知⊙O的弦AB=8cm,圆心O到弦AB的距离为3cm,则⊙O的直径为____ cm.
导致两极地区冰川融化,海平面上升的主要原因是( )
—For one week.But it mustn't ________ to others.