Paul is walking up and down.的意思是：保罗上下走来走去。其中walking的意思是：步行，散步，up and down的意思是：上上下下，起落。
拓展资料
up and down
1、All up and down the street the windows bang shut
整条街的窗户都砰然关上了。
2、He learned to walk safely up and down stairs
他学会了安全地上下楼梯。
3、Then I noticed the car was bouncing up and down as if someone were jumping on it
然后我注意到那辆车在上下颠簸，好像有人在车上蹦跳似的。
4、He looked up and down the corridor, meaty hands resting on his thighs.
他两只胖乎乎的手搁在大腿上，上下打量着这个走廊。
5、They came into the front hall, stamping their boots and jumping up and down to knock the snow off
他们进入了前厅，跺着靴子，蹦跳着抖掉身上的雪。
6、The performers, in costume and make-up, were walking up and down backstage
上了妆穿着戏服的演员在后台走来走去。
7、He continued to jump up and down like a boy at a football match
他不停地上蹿下跳，活像个足球赛中的男孩。
8、There's a lot of rushing up and down the gangways.
舷梯上许多人上上下下。
