孩子们在楼梯上跑来跑去。
The children ran ___up ___and ___down the stairs.
节日期间，人们在街道上来回走动。
People were moving ___up ___and ___down the street during the festival.
她在房间里来回踱步，深思熟虑。
She paced ___up ___and ___down the room, thinking deeply.