and if you're really on a roll, you can hit the W key for "whiteout," and you white out the slide, and then you can hit W again to un-blank it.
你再按下B键，接着如果你真很顺利的话， 你可以按W键，让屏幕全白。 你这样子做了，然后你可以再按下W键， 恢复回来。